English

• 0.   Introduction

  Supramolecular coordination complexes (SCCs) are discrete molecular entities formed through the self-assembly of metal ions or metal clusters and ligands^[1-2]. These complexes represent a fusion of inorganic and supramolecular chemistry, focusing on self-assembled systems in which metal-based units are connected via coordination bonds and other intermolecular interactions. SCCs integrate the common characteristics of both coordination and supramolecular complexes, not only incorporating the diverse physical and chemical properties of metal ions/clusters, but also introducing well-established methodologies of organic synthesis and versatile strategies for structural design and modification. This synergy offers more choices for the rapid development of supramolecular synthesis technologies. As a result, SCCs demonstrate outstanding performance across multiple fields, including optics^[3], proton conductivity^[4-5], magnetism^[6], catalysis^[7-9], host-guest chemistry^[10-11], gas storage and separation^[12-13], nanoreactors^[14-15], drug delivery^[16-17], and molecular sensing^[18-19].

  Calixarenes are a classic class of macrocyclic complexes with cavity structures, composed of multiple phenol units connected through bridging groups at the ortho positions of the phenolic hydroxyl groups^[20-21]. Due to their unique chemical structures and rich physical/chemical properties, calixarenes represent the third generation of supramolecular host compounds, following crown ethers and cyclodextrins. p-Sulfosulfonylcalix[4]arene (H₈TC4AS-SO₂)^[22-24], a subclass of the calix[n]arene family, features sulfonate groups at the upper rim, four phenolic hydroxyl oxygen atoms at the lower rim, and sulfonyl bridging groups, providing multiple coordination sites for the construction of novel structures with metal ions^[25-35]. Meanwhile, metal ions can also coordinate with auxiliary ligands possessing multiple coordination sites, thereby forming novel supramolecular complexes with diverse structures.

  It is well known that in the construction of coordination complexes, besides the main and auxiliary ligands, the type of solvent also exerts a significant influence on the crystallization process, coordination geometry, and final structure of the coordination complexes, such as the polarity, volume ratio, proticity, coordination ability, and hydrogen-bonding interactions with ligands of solvent^[36-40]. For example, when constructing supramolecular architectures employing TC4AS-SO₂ as the main ligand, altering the solvent types can effectively change the way the main ligand coordinates, resulting in a variety of novel structures^[25-35]. Under aqueous solvent conditions, the main ligand adopts diverse coordination behaviors: through the upper rim, the lower rim, or both edges simultaneously, giving rise to diverse zero-dimensional low-core cluster structures^[25-27]. However, using methanol as a solvent enables TC4AS-SO₂ to coordinate with transition metals, yielding an anionic {Co₂₄} coordination cage^[28-35].

  Inspired by the significant influence of solvent regulation on the construction of calixarene-based complexes and the diverse coordination modes of functional auxiliary ligands, this work employs H₈TC4AS-SO₂ as the main ligand and thiophene-2,5-dicarboxylic acid (H₂TDC) as a bridging ligand. These components react with Co²⁺ ions under solvothermal conditions. The present study aims to construct multifunctional coordination cage complexes through a synthetic approach analogous to that employed for p-tert-butylsulfonylcalix[4]arene (H₄TC4A-SO₂), auxiliary ligands, and metal ions^[41]. Remarkably, solvent modulation led to the successful synthesis of both 2D layers and 3D network architectures, in which the upper and lower rims of (H₄TC4AS-SO₂)^4-, as well as TDC^2-, participate in coordination with cobalt metal ions (Scheme 1). Methanol with relatively high polarity promotes the formation of layered structures, resulting in {[(CH₃)₄N]₄[Co₃(μ₃-O)(H₄TC4AS-SO₂)]₂(TDC)₂·2H₂O·67CH₃OH}_n (denoted LLU-101, LLU=Lyuliang University), while DMF with lower polarity facilitates the assembly of more compact and interconnected 3D frameworks: {[(CH₃)₄N]₂[Co₃(μ₄-O)(H₄TC4AS-SO₂)_0.5(TDC)₂]·32DMF}_n (LLU-102). The syntheses, structures, and magnetic properties of these complexes are reported and discussed herein.

  Scheme 1

  

  Scheme 1.  Synthetic route of LLU-101 and LLU-102

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  1.   Experimental

  1.1   Materials and physical measurements

  H₈TC4AS-SO₂ was prepared according to the reported synthetic methods in the literature^[22-24]. The synthetic procedure is provided in the Supporting information, and the corresponding synthetic route is illustrated in Fig.S1 and S2. H₂TDC was purchased from Aladdin Reagent Company. Other commercial reagents and raw materials used in this study were all of analytical grade and were directly used without further purification. Elemental analysis (C, H, S) was carried out on a Perkin-Elmer 2400 elemental analyzer. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDS) mapping were obtained using a Zeiss Sigma 300, Oxford Instruments Xplore30 spectrometer. The thermogravimetric (TG) curve was determined on a Netzsch STA 449F3 thermogravimetric analyzer under an air atmosphere with a heating rate of 10 ℃·min^-1, from room temperature to 800 ℃. Fourier transform infrared spectroscopy (FTIR) was measured using a Bruker IFS 66V/SFT/IR infrared spectrometer in the range of 400-4 000 cm^-1 with KBr pellets. Variable-temperature magnetic susceptibility was measured using a Quantum Design MPMS XL-5/7 SQUID instrument at a fixed magnetic field strength of 1000 Oe, with the temperature range from 2.0 to 300 K. Single-crystal X-ray diffraction analysis was performed on a Bruker D8 QUEST (Cu Kα, λ=0.154 178 nm) single-crystal diffractometer from Bruker AXS GmbH, Germany.

  1.2   Synthesis of LLU-101

  H₈TC4AS-SO₂ (0.047 g, 0.05 mmol), CoCl₂·6H₂O (0.05 g, 0.2 mmol), CoSO₄·7H₂O (0.03 g, 0.11 mmol), H₂TDC (0.026 g, 0.15 mmol), tetramethylammonium bromide (0.01 g, 0.06 mmol), and CH₃OH (2.0 mL) were mixed evenly and then transferred successively into a 20 mL stainless steel autoclave with a polytetrafluoroethylene lining. The autoclave lid was immediately screwed on, and the mixture was heated at 130 ℃ for 72 h in a constant temperature oven. Then, it was slowly cooled to room temperature at a rate of 4 ℃·h^-1, and red block crystals of LLU-101 were obtained. The crystals were separated and collected by filtration, washed with CH₃OH solvent, and dried in air, with a yield of approximately 43% (based on H₈TC4AS-SO₂). The molecular formula of complex LLU-101 analyzed was {[(CH₃)₄N]₄[Co₃(μ₃-O)(H₄TC4AS-SO₂)]₂(TDC)₂·2H₂O·67CH₃OH}_n. Elemental analysis Calcd. for C₁₄₃H₃₄₈Co₆O₁₂₇N₄S₁₈(%): C 33.76, H 6.90, S 11.35, N 1.10; Found(%): C 32.85, H 6.14, S 11.36, N 1.45. FTIR (cm^-1): 3 429 (w), 2 962 (s), 2 868 (w), 1 654 (m), 1 554 (w), 1 528 (w), 1 479 (w), 1 458 (m), 1 441 (w), 1 385 (s), 1 305 (m), 1 281 (w), 1 257 (s), 1 232 (w), 1 135 (m), 966 (w), 902 (w), 890 (s), 837 (s), 800 (m), 768 (m), 749 (s), 736 (w), 636 (w), 616 (m), 544 (m) (Fig.S3a).

  1.3   Synthesis of LLU-102

  LLU-102 was synthesized using the same method as LLU-101, except N,N-dimethylformamide (DMF) (2.0 mL) was used instead of methanol. Light red block crystals of LLU-102 were obtained. The crystals were separated by filtration, washed with DMF, and dried in air, with a yield of 44% (based on H₈TC4AS-SO₂). The molecular formula of complex LLU-102 was {[(CH₃)₄N]₂[Co₃(μ₄-O)(H₄TC4AS-SO₂)_0.5(TDC)₂]·32DMF}_n. Elemental analysis Calcd. for C₁₂₈H₂₅₈Co₃O₅₃N₃₄S₆(%): C 44.04, H 7.45, S 5.51, N 13.64; Found(%): C 42.85, H 7.40, S 4.88, N 13.62. FTIR (cm^-1): 3 432 (w), 1 659 (m), 1 559 (s), 1 478 (m), 1 436 (w), 1 381 (w), 1 312 (m), 1 261 (w), 1 187 (m), 1 139 (m), 1 038 (s), 948 (s), 881 (s), 778 (w), 767 (w), 756 (m), 718 (m), 623 (s), 528 (w) (Fig.S3b).

  1.4   Single-crystal X-ray diffraction

  The single-crystal diffraction data of complexes LLU-101 and LLU-102 were collected using a Bruker D8 QUEST (Cu Kα, λ=0.154 178 nm) instrument, and the diffraction data were subjected to reduction and absorption correction. The crystal structures of complexes were solved by the direct method and refined by the full-matrix least-squares method based on F ² (SHELXL-2025)^[42-44]. All non-hydrogen atoms in the crystal structures were refined anisotropically. For the carbon atoms in the structures, theoretical hydrogen atoms were added using a riding model, while for nitrogen and oxygen atoms, hydrogen atoms were added manually. Some disordered solvent molecules in the structures of complexes LLU-101 and LLU-102 could not be located and were processed using the “SQUEEZE” command in the PLATON software to remove the unidentified solvent molecules from the structures^[45]. The crystal refinement parameters are shown in Table 1. The selected bond lengths and angles of complexes LLU-101 and LLU-102 are illustrated in Table S1 and Table S2.

  Table 1

  

  Table 1.  Crystal data and structure refinement for LLU-101 and LLU-102

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  Parameter	LLU-101	LLU-102
  Formula	C143H348Co6O127N4S18	C128H258Co3O53N34S6
  Formula weight	5 087.01	3 490.80
  Crystal system	Triclinic	Tetragonal
  Space group	P1	P4/n
  a / nm	1.485 74(9)	1.881 63(3)
  b / nm	2.164 55(13)	1.881 63(3)
  c / nm	2.603 35(19)	3.061 92(7)
  α / (°)	91.901(4)
  β / (°)	99.687(4)
  γ / (°)	101.781(4)
  V / nm3	8.059 2(9)	10.840 8(4)
  Z	2	8
  T / K	190	190
  Dc / (g·cm-3)	1.212	1.409
  μ / mm-1	7.536	9.863
  F(000)	2 988	4 664
  Total reflection	23 880	50 472
  Unique reflection	3 029	1 233
  Rint	0.189 7	0.104 0
  GOF	1.134	1.371
  Final R indices [I>2σ(I)]	R1=0.165 9, wR2=0.342 2	R1=0.149 6, wR2=0.292 7
  R indices (all data)	R1=0.213 0, wR2=0.366 4	R1=0.160 3, wR2=0.299 3
  aR1=∑||Fo|-|Fc||/∑|Fo|; bwR2=∑[w(Fo2-Fc2)2]/∑[w(Fo2)2]1/2.

  2.   Results and discussion

  2.1   Crystal structure of LLU-101

  Complex LLU-101 crystallizes in the triclinic system, with the space group P1. As shown in Fig.S4 and S5, complex LLU-101 forms a 2D layered structure through the bridging of {Co₃-H₄TC4AS-SO₂} secondary building units (SBUs) (Fig. 1a) and TDC^2- units (Fig. 1b). Three adjacent Co²⁺ ions form a triangular planar Co₃ cluster, and the Co²⁺ ions are connected by three phenolic hydroxyl oxygen atoms at the bottom end and one oxygen atom from the bridging sulfonyl group of the (H₄TC4AS-SO₂)^4- ion. {Co₃-H₄TC4AS-SO₂} SBU exhibits a cone conformation, resembling a shuttlecock with the bottom of the three adjacent Co²⁺ ions capped by a μ₃-O atom (Fig. 1a). As illustrated in Fig. 1c, each Co²⁺ ion adopts a distorted octahedral coordination geometry. However, the Co²⁺ ions have two coordination environments: Co1 and Co3 share the same coordination environment, involving two phenolic hydroxyl oxygen atoms from (H₄TC4AS-SO₂)^4-, one oxygen atom of the bridging sulfonyl group, one μ₃-O oxygen atom, one oxygen atom from the bridging ligand TDC^2-, and one oxygen atom from the sulfonate group at the upper rim in the adjacent (H₄TC4AS-SO₂)^4- ion. In contrast, Co2 differs from Co1 and Co3 in that it is not coordinated with the sulfonate oxygen atom from the upper rim of (H₄TC4AS-SO₂)^4-, but is coordinated with an oxygen atom from another bridging ligand TDC^2-. As shown in Table S3, according to the valence bond sum theory calculation, all metal cobalt ions in this complex are divalent^[46-48]. Each {Co₃-H₄TC4AS-SO₂} SBU, as a vertex, is connected in a four-connected manner to two bridging ligands TDC^2- and the sulfonate groups at the upper rim in two other (H₄TC4AS-SO₂)^4- ions (Fig. 1c), while each bridging ligand TDC^2-, as a two-connected linear edge, connects two {Co₃-H₄TC4AS-SO₂} SBUs through the carboxyl oxygen atoms in the TDC^2- ligand (Fig. 1d). Therefore, each asymmetric unit consists of two {Co₃-H₄TC4AS-SO₂} SBUs and two bridging ligands TDC^2-, forming a complete structural unit (Fig. 1e and 1f).

  Figure 1

  

  Figure 1.  Views of the structure of LLU-101: (a) structure of the shuttlecock-like {Co₃-H₄TC4AS-SO₂} unit; (b) structure diagram of TDC^2-; (c) one shuttlecock-like {Co₃-H₄TC4AS-SO₂} and two TDC^2- ligands; (d) two shuttlecock-like {Co₃-H₄TC4AS-SO₂} units and one TDC^2- ligand; (e) schematic diagram of the asymmetric unit; (f) schematic diagram of the bowl-shaped asymmetric unit

  The hydrogen atoms are removed for clarity.

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  The asymmetric unit shown in Fig. 1e and 1f contains carboxylate groups from the TDC^2- ligands on both the left and right sides of the supramolecular structure containing four {Co₃-H₄TC4AS-SO₂} SBUs (red circles in Fig. 2a), as well as coordination sites formed by the coordination between the metal Co ions and the sulfonate groups at the upper rim of (H₄TC4AS-SO₂)^4- (light blue circles in Fig. 2a). These coordination sites are equivalent to one (H₄TC4AS-SO₂)^4- ion, facilitating their connection to form shuttlecock-like structures in an “upper-lower” arrangement (Fig. 2d). The “upper-lower” shuttlecock-like structures can further connect on both sides, resulting in the formation of multiple “upper-lower” shuttlecock-like units (the middle parts of Fig. 2b and 2c). The “upper-lower” shuttlecock-like structures are linked to TDC^2- ligands above and below, and the carboxylate groups of the TDC^2- ligands continue to connect with the {Co₃-H₄TC4AS-SO₂} SBU, allowing the structure to extend repetitively in a 2D manner.

  Figure 2

  

  Figure 2.  Views of the extended structures of LLU-101: (a) schematic diagram of the exposed coordination sites of the shuttlecock-like {Co₃-H₄TC4AS-SO₂} and four TDC^2- ligands; (b) schematic diagram of the exposed coordination sites of multiple “upper-lower” shuttlecock-like structures and their TDC^2- ligands; (c) schematic diagram of the extended connection between multiple “upper-lower” shuttlecock-like structures and the TDC^2- ligands to the shuttlecock-like {Co₃-H₄TC4AS-SO₂} SBUs; (d) schematic diagram of the “upper-lower” shuttlecock-like SBU dimers with π-π interactions

  The hydrogen atoms are removed for clarity.

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  As shown in Fig.S4 and S5, viewed along the a-axis direction of the unit cell, the 2D layers stack on top of each other through non-covalent interactions and a shape match between the two shuttlecock units of opposite orientations in adjacent layers. This packing mode still leaves some gaps between the adjacent layers due to the irregular shape of the shuttlecock-like SBUs.

  2.2   Crystal structure of LLU-102

  Complex LLU-102 crystallizes in the tetragonal system, with the space group P4/n. As illustrated in Fig. 3, in the structure of LLU-102, four adjacent cobalt ions form a square-planar Co₄ nuclear cluster and are connected by four phenolic hydroxyl oxygen atoms at the lower end and two oxygen atoms from the bridging sulfonyl group of the (H₄TC4AS-SO₂)^4- ion in a cone conformation. Finally, a {Co₄-H₄TC4AS-SO₂} SBU resembling a shuttlecock is formed, with the bottom of the four adjacent cobalt ions capped by a μ₄-O atom (Fig. 3a). As depicted in Fig. 3c and 3d, each central Co²⁺ ion in this structure adopts a distorted octahedral geometry. However, the Co ions exhibit two distinct coordination environments. Taking Co1 as an example, the coordination environment of the four Co²⁺ ions at the bottom of the shuttlecock-like {Co₄-H₄TC4AS-SO₂} is coordinated by two phenolic hydroxyl oxygen atoms and two oxygen atoms of the bridging sulfonyl group from (H₄TC4AS-SO₂)^4-, one μ₄-O oxygen atom, and one oxygen atom from the bridging ligand TDC^2-. In contrast, the coordination environment of Co2 in the structure is as follows: it is coordinated by two oxygen atoms from one bridging ligand TDC^2-, two oxygen atoms from another two bridging ligands TDC^2-, one μ₂-O oxygen atom, and an oxygen atom from the sulfonate group at the upper rim of (H₄TC4AS-SO₂)^4-. As seen from Table S4, according to the valence bond theory calculation, all metal cobalt ions in this complex are divalent^[46-48]. Each {Co₄-H₄TC4AS-SO₂} SBU, as a vertex, is connected to four bridging ligands TDC^2- in a four-connected manner (Fig. 3c). Each bridging ligand TDC^2- has two different coordination environments. From Fig. 3e, it is shown that the carboxylate oxygen atoms at one end of the bridging ligand TDC^2- are all monodentately coordinated, connecting with two different Co²⁺ ions, while the carboxylate oxygen atoms at the other end are also monodentately coordinated, but coordinated with a single Co²⁺ ion. Fig. 3f demonstrates that the carboxylate oxygen atoms at both ends of the bridging ligand TDC^2- have the same coordination mode, meaning they are respectively coordinated with different metal center Co²⁺ ions.

  Figure 3

  

  Figure 3.  Views of the extended structures of LLU-102: (a) diagram of the shuttlecock-like {Co₄-H₄TC4AS-SO₂} unit; (b) structure diagram of TDC^2-; (c) one shuttlecock-like {Co₄-H₄TC4AS-SO₂} and four TDC^2- ligands; (d) two shuttlecock-like {Co₄-H₄TC4AS-SO₂} units and four TDC^2- ligands; (e) schematic diagram of the first coordination mode of TDC^2-; (f) schematic diagram of the second coordination mode of TDC^2-

  The hydrogen atoms are removed for clarity.

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  As shown in Fig. 4a, a “hierarchical” layer is formed through the four-connected mode of {Co₄-H₄TC4AS-SO₂} SBUs, the diverse coordination modes of the bridging ligand TDC^2-, the varying coordination environments of the metal center Co²⁺ ions, and the coordination characteristics of the oxygen atoms in the sulfonate groups at the upper rim of (H₄TC4AS-SO₂)^4-. This “hierarchical” structure is further connected by the segments illustrated in Fig. 4b-4d. In this arrangement, each {Co₄-H₄TC4AS-SO₂} SBU is connected to four bridging ligands, TDC^2-. Then, the TDC^2- ligands are connected to the Co²⁺ ions, which continue to coordinate with the oxygen atoms in the sulfonate groups at the upper rim of (H₄TC4AS-SO₂)^4-, forming a “capsule-like” structure of double {Co₄-H₄TC4AS-SO₂} SBUs (Fig. 4b). The metal centers in the coordination environment of two Co2 ions are connected to four TDC^2- ligands and two {Co₄-H₄TC4AS-SO₂} SBUs on both sides, resulting in a “balance pan” structure of double {Co₄-H₄TC4AS-SO₂} SBUs (Fig. 4c). The tetracoordination formed by the sulfonate oxygen atoms at the upper rim of the {Co₄-H₄TC4AS-SO₂} SBU and the four-connected mode formed by the TDC^2- ligands at the bottom end endow the {Co₄-H₄TC4AS-SO₂} SBU with an eight-connected mode. The four TDC^2- ligands at the lower end continue to connect four inverted {Co₄-H₄TC4AS-SO₂} SBUs through the Co²⁺ ions, finally forming a “four-wheel” structure (Fig. 4d).

  Figure 4

  

  Figure 4.  (a) Schematic diagram of the bowl-shaped “hierarchical” structure formed by LLU-102; (b) Schematic diagram of the bowl-shaped “capsule-like” structure of double {Co₄-H₄TC4AS-SO₂} SBUs formed by LLU-102; (c) Schematic diagram of the bowl-shaped “balance pan” structure of double {Co₄-H₄TC4AS-SO₂} SBUs formed by LLU-102; (d) Schematic diagram of the bowl-shaped “four-wheel” structure

  The hydrogen atoms are removed for clarity.

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  As depicted in Fig.S6 and S7, the “capsule-like”, “balance pan”, and the “four-wheel” structures are interconnected to form a unified “hierarchical” network. Due to the supramolecular interactions between the molecules of the formed “hierarchical” structure, a non-covalent 3D network structure with a tightly combined “hierarchy” is finally formed. LLU-102 forms a tightly packed structure, leaving a small channel of 0.42 nm×0.33 nm running along the (110) direction (Fig.S8).

  2.3   Structural characteristics of complexes LLU-101 and LLU-102

  We further investigated the structural characteristics of complexes LLU-101 and LLU-102. As shown in Fig. 5, under varying solvent conditions, the (H₄TC4AS-SO₂)^4- ions and H₂TDC bridging ligands in these two complexes exhibit multiple coordination modes, resulting in distinct structural features for LLU-101 and LLU-102. In the structure of LLU-101, three phenolic hydroxyl oxygen atoms at the lower rim of the (H₄TC4AS-SO₂)^4- ion and the oxygen atoms from three bridging sulfonyl groups coordinate with three Co²⁺ ions, forming a {Co₃} trinuclear cluster (Fig. 5a). However, in the structure of LLU-102, four phenolic hydroxyl oxygen atoms at the lower rim of the (H₄TC4AS-SO₂)^4- ion and the oxygen atoms from four bridging sulfonyl groups coordinate with four Co²⁺ ions, forming a square {Co₄} tetranuclear cluster (Fig. 5b and 5c).

  Figure 5

  

  Figure 5.  (a) Schematic diagram of the coordination mode of (H₄TC4AS-SO₂)^4- in the structure of complex LLU-101; (b, c) Schematic diagrams of the coordination mode of (H₄TC4AS-SO₂)^4- in the structure of complex LLU-102

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  Moreover, at the bottom of the shuttlecock-like SBU, a bridging oxygen atom is present, but with different coordination modes. In LLU-101, the oxygen atom is μ₃-O, while in LLU-102, it is μ₄-O. In addition, in LLU-101, the oxygen atoms from two sulfonate groups at the upper rim of the (H₄TC4AS-SO₂)^4- ion coordinate with two Co²⁺ ions, and the angle formed between these metal ions and the coordinated oxygen and sulfur atoms is 137° (Fig. 5a). In contrast, in LLU-102, the sulfonate groups at the upper rim of the (H₄TC4AS-SO₂)^4- ion exhibit two coordination modes. The first mode, shown in Fig. 5b, is that the sulfonate groups at the upper rim do not coordinate with the metal. The second mode, depicted in Fig. 5c, is that one oxygen atom in each of the four sulfonate groups at the upper rim coordinates with the Co²⁺ ion, forming an angle of 132° with the coordinated oxygen and sulfur atoms.

  Furthermore, the coordination modes of the bridging ligands differ between the two complexes. In LLU-101, the TDC^2- ligand coordinates as shown in Fig. 1d. Methanol, with higher polarity compared to DMF, allows more open coordination geometries, which are further stabilized and favored for the formation of a layered architecture through extensive hydrogen bonding and π-π intermolecular interactions. In contrast, LLU-102, crystallized in DMF, exhibits two distinct coordination modes for TDC^2-, which are depicted in Fig. 3e and 3f. DMF fosters a diverse array of coordination connections for the auxiliary ligands and, through a combination of hydrogen bonding and π-π interactions, ultimately promotes the formation of a compact 3D framework.

  Based on the structures discussed above, it can be concluded that variations in solvent polarity directly govern the coordination modes of the (H₄TC4AS-SO₂)^4- ligand and the bridging TDC^2- ligand, thereby ultimately influencing the packing of the SBUs in LLU-101 and LLU-102. Furthermore, two complexes were compared and analyzed with the reported relevant Co-TC4AS-SO₂-based supramolecular coordination complexes. The results indicate that TC4AS-SO₂, as the main ligand, typically coordinates with cobalt ions to form {Co₄} SBU, which then coordinates with various auxiliary ligands to form a series of zero-dimensional {Co₂₄} organic coordination cages (Fig.S9)^[28-35]. In these architectures, the sulfonate groups located on the upper rim of the main ligand remain uncoordinated. Additionally, complexes LLU-101 and LLU-102 were compared with the previously reported complex CIAC-122^[41], which has the same auxiliary ligands (TDC^2-), but a different main ligand is altered from TC4AS-SO₂ to p-tert-butylsulfonylcalix[4]arene (TC4A-SO₂). This modification ultimately results in the formation of a triangular {Co₁₂} coordination cage in CIAC-122, in which the auxiliary ligands exhibit bidentate coordination and bind to four cobalt ions (Fig.S10).

  It is noteworthy that earlier studies report that sulfonic acid groups incorporated at the upper rim of calixarenes, designed to provide additional coordination sites, usually remain non-coordinating toward cobalt. In contrast, the present study identifies a solvent-dependent deviation from this precedent, wherein the main ligand exhibits alternative coordination modes, accompanied by the emergence of novel coordination behaviors in the auxiliary ligands. This solvent-mediated modulation of ligand coordination capacity deepens the understanding of metal-calixarene and provides a theoretical foundation for the rational design of coordination architectures with tunable dimensionality.

  2.4   SEM-EDS and TG analysis of complexes LLU-101 and LLU-102

  As illustrated in Fig.S11 and S12, the SEM images and EDS mapping have been obtained to observe the surface morphology and elemental composition of LLU-101 and LLU-102. SEM analysis reveals that LLU-101 exhibited a layered, sheet-like morphology of the obtained crystals, whereas LLU-102 displayed a rod-like morphology with a honeycomb surface texture. EDS mapping confirmed the presence and uniform distribution of Co, S, O, and C within both LLU-101 and LLU-102, thereby substantiating their successful synthesis and the integrity of their structural frameworks.

  Complexes LLU-101 and LLU-102 were subjected to TG measurement in an air atmosphere with the temperature ranging from 25 to 800 ℃. As shown in Fig.S13, the TG curves of LLU-101 and LLU-102 reveal that both complexes experienced an initial weight loss before 305 and 340 ℃, respectively. This initial weight loss can be attributed to the evaporation of solvent molecules from the crystals. As the temperature increased, a second weight loss stage occurred for both complexes, with LLU-101 losing weight between 305 and 505 ℃ and LLU-102 between 340 and 525 ℃. The weight loss is primarily due to the decomposition of the complexes′ frameworks. Complexes LLU-101 and LLU-102 reached the weight-loss equilibrium in the temperature range from 505 or 525 ℃ to 800 ℃, with no further weight changes. Ultimately, the remaining black powder was identified as cobalt oxides. The TG analysis further indicates that LLU-101 and LLU-102 exhibit good thermal stability, which may be attributed to the rigid coordination environment of the metal center, the high-dimensional structure, and the extensive hydrogen bonding and π-π interactions within the crystal^[5,49].

  2.5   Magnetic properties of complexes LLU-101 and LLU-102

  Variable-temperature direct-current magnetic susceptibility measurements for complexes LLU-101 and LLU-102 were conducted in the temperature range of 2-300 K under an applied magnetic field strength of 1 kOe. As shown in Fig. 6a and 6b, the χ_mT values of LLU-101 and LLU-102 at room temperature were 9.43 and 19.3 cm³·mol^-1·K, respectively. These values exceeded the theoretical values for LLU-101 or LLU-102 containing high-spin Co²⁺ ions (S=3/2, g=2.0) without coupling interaction (15/8×3=5.63 cm³·mol^-1·K for LLU-101, 15/8×6=11.25 cm³·mol^-1·K, for LLU-102). This discrepancy may be attributed to spin-orbit coupling with the Co²⁺ ions and the distorted octahedral field^[50]. For each Co²⁺ ion, the χ_mT values of LLU-101 and LLU-102 at room temperature were 3.14 and 3.22 cm³·mol^-1·K, respectively. Variable-temperature magnetic susceptibility values of the reported typical compounds containing Co²⁺ ions were in a range of 2.7 to 3.4 cm³·mol^-1·K^[51]. As the temperature decreased, the χ_mT curves of LLU-101 and LLU-102 decreased gradually and exhibited a sharp decline in the low-temperature region. When the temperature was 2 K, the χ_mT values reached the minimum values of 0.23 and 4.88 cm³·mol^-1·K, respectively. The progressive diminution of χ_mT over the temperature range from 300 to 2 K is indicative of pronounced antiferromagnetic coupling inherent within the molecular architecture^[52-54]. In the 50-300 K range, the variable-temperature magnetic susceptibility curves of LLU-101 and LLU-102 conformed to the Curie-Weiss law: 1/χ_m=(T-θ)/C. The calculated Curie constants (C) were 10.54 and 20.81 cm³·K·mol^-1, and the Weiss constants (θ) were -34.72 and -26.58 K, respectively. The negative Weiss constant indicates an overall antiferromagnetic interaction between the metal ions, consistent with the small ground-state spin value of the complexes^[51,54].

  Figure 6

  

  Figure 6.  Variable-temperature magnetic susceptibility curves of complex LLU-101 (a) and complex LLU-102 (b) in the temperature range of 2-300 K

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  Among these two complexes, LLU-101 exhibits a 2D structure, whereas LLU-102 adopts a 3D structure. These two structures also differ in their SBUs. LLU-101 contains a planar triangular Co²⁺ trimer (Fig.S14), while LLU-102 features both a planar quadrilateral Co²⁺ tetramer and a linear Co²⁺ dimer (Fig.S15). In each triangular, quadrilateral, or linear cluster, Co²⁺ centers are linked via oxygen atoms, forming the respective cluster units. This type of interaction pathway (Co-O-Co) fosters strong superexchange interactions between the magnetic Co²⁺ ions, owing to the effective overlap of the Co²⁺ 3d orbitals through the 2p orbitals of oxygen atoms^[55-57]. Consequently, due to the structural similarity of their lattices, one would expect nearly identical magnetic behavior for LLU-101 and LLU-102. Indeed, the θ values for LLU-101 were relatively smaller, while LLU-102 exhibited larger θ values. These observations align closely with their respective structural features. Furthermore, in both LLU-101 and LLU-102, the Co²⁺ centers exhibit a distorted octahedral coordination geometry. This distortion induces significant orbital angular momentum and spin-orbit coupling, thereby resulting in the splitting of the d-orbitals^[57]. As a result, the metal centers in both compounds exhibit antiferromagnetic interactions.

  These observations indicate that the variation in solvent polarity not only alters the coordination modes of the TDC^2- and (H₄TC4AS-SO₂)^4- ligands but also governs the nuclearity of the metal clusters, which play a pivotal role in tuning the intracluster and intercluster magnetic exchange interactions^[52-53], ultimately leading to the distinct magnetic properties observed for LLU-101 and LLU-102. The relationship between structure and magnetic properties is summarized and compared in Table S5. In the cobalt-based supramolecular complexes constructed with calixarene-type ligands, regardless of the nuclearity, the measured Weiss constants are consistently negative, indicating that the cobalt metal centers exhibit antiferromagnetic interactions.

  3.   Conclusions

  In this study, p-sulfosulfonylcalix[4]arene (H₈TC4AS-SO₂) was used as the main ligand, and thiophene-2,5-dicarboxylic acid (H₂TDC) was introduced as the bridging ligand to react with transition metal Co²⁺ ions. Two cluster-based extended structures, LLU-101 and LLU-102, were successfully constructed, with both the upper and lower rims of (H₄TC4AS-SO₂)^4- being coordinated and connected through TDC^2-. The solvent type during the solvothermal reactions significantly influences the final structure of the complexes. In the case of LLU-101, synthesized using methanol as the solvent, the shuttlecock-like unit formed is a trinuclear cobalt {Co₃-H₄TC4AS-SO₂}, with both the upper and lower rims of (H₄TC4AS-SO₂)^4- participating in coordination, and a single mode of the TDC^2- ligand. On the other hand, when synthesized under DMF conditions, LLU-102 formed a shuttlecock-like unit, a tetranuclear cobalt {Co₄-H₄TC4AS-SO₂}, where both the upper and lower rims of (H₄TC4AS-SO₂)^4- are coordinated, some SBUs display coordination involving only the lower rim, and two different coordination modes of TDC^2- ligands. The study on the magnetic properties of complexes LLU-101 and LLU-102 shows that the metal centers exhibit antiferromagnetic interactions and that solvent choice plays a pivotal role in tuning both structural features and magnetic interactions. This work is expected to provide valuable insights for the design and synthesis of other sulfonylcalixarene tetrasulfonate-derived complexes based on a solvent regulation strategy. This will facilitate the exploration of their potential applications based on defined structure-property relationships.

  
  Acknowledgments: The current work was supported by the Science and Technology Innovation Program for Higher Education Institutions in Shanxi Province of the Education Department of Shanxi Province (Grant No.2023L370), the High-level Scientific and Technological Talents Project of Lüliang City (Grant No.2023RC23), supported by Fundamental Research Program of Shanxi Province (Grant No.202203021222317), Shanxi Provincial College Students' Innovation and Entrepreneurship Program, Lyuliang University (Grant No.S202510812003), Open Project of State Key Laboratory of Inorganic Synthesis and Preparative Chemistry (Grant No.2026-26), and the Doctoral Scientific Research Start-up Fund of Lyuliang University. Conflicts of interest: All authors claimed no competing interests.
  Supporting information is available at http://www.wjhxxb.cn
  
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• 

  Scheme 1  Synthetic route of LLU-101 and LLU-102

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  Figure 1  Views of the structure of LLU-101: (a) structure of the shuttlecock-like {Co₃-H₄TC4AS-SO₂} unit; (b) structure diagram of TDC^2-; (c) one shuttlecock-like {Co₃-H₄TC4AS-SO₂} and two TDC^2- ligands; (d) two shuttlecock-like {Co₃-H₄TC4AS-SO₂} units and one TDC^2- ligand; (e) schematic diagram of the asymmetric unit; (f) schematic diagram of the bowl-shaped asymmetric unit

  The hydrogen atoms are removed for clarity.

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  Figure 2  Views of the extended structures of LLU-101: (a) schematic diagram of the exposed coordination sites of the shuttlecock-like {Co₃-H₄TC4AS-SO₂} and four TDC^2- ligands; (b) schematic diagram of the exposed coordination sites of multiple “upper-lower” shuttlecock-like structures and their TDC^2- ligands; (c) schematic diagram of the extended connection between multiple “upper-lower” shuttlecock-like structures and the TDC^2- ligands to the shuttlecock-like {Co₃-H₄TC4AS-SO₂} SBUs; (d) schematic diagram of the “upper-lower” shuttlecock-like SBU dimers with π-π interactions

  The hydrogen atoms are removed for clarity.

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  Figure 3  Views of the extended structures of LLU-102: (a) diagram of the shuttlecock-like {Co₄-H₄TC4AS-SO₂} unit; (b) structure diagram of TDC^2-; (c) one shuttlecock-like {Co₄-H₄TC4AS-SO₂} and four TDC^2- ligands; (d) two shuttlecock-like {Co₄-H₄TC4AS-SO₂} units and four TDC^2- ligands; (e) schematic diagram of the first coordination mode of TDC^2-; (f) schematic diagram of the second coordination mode of TDC^2-

  The hydrogen atoms are removed for clarity.

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  Figure 4  (a) Schematic diagram of the bowl-shaped “hierarchical” structure formed by LLU-102; (b) Schematic diagram of the bowl-shaped “capsule-like” structure of double {Co₄-H₄TC4AS-SO₂} SBUs formed by LLU-102; (c) Schematic diagram of the bowl-shaped “balance pan” structure of double {Co₄-H₄TC4AS-SO₂} SBUs formed by LLU-102; (d) Schematic diagram of the bowl-shaped “four-wheel” structure

  The hydrogen atoms are removed for clarity.

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  Figure 5  (a) Schematic diagram of the coordination mode of (H₄TC4AS-SO₂)^4- in the structure of complex LLU-101; (b, c) Schematic diagrams of the coordination mode of (H₄TC4AS-SO₂)^4- in the structure of complex LLU-102

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  Figure 6  Variable-temperature magnetic susceptibility curves of complex LLU-101 (a) and complex LLU-102 (b) in the temperature range of 2-300 K

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  Table 1.  Crystal data and structure refinement for LLU-101 and LLU-102

  Parameter	LLU-101	LLU-102
  Formula	C143H348Co6O127N4S18	C128H258Co3O53N34S6
  Formula weight	5 087.01	3 490.80
  Crystal system	Triclinic	Tetragonal
  Space group	P1	P4/n
  a / nm	1.485 74(9)	1.881 63(3)
  b / nm	2.164 55(13)	1.881 63(3)
  c / nm	2.603 35(19)	3.061 92(7)
  α / (°)	91.901(4)
  β / (°)	99.687(4)
  γ / (°)	101.781(4)
  V / nm3	8.059 2(9)	10.840 8(4)
  Z	2	8
  T / K	190	190
  Dc / (g·cm-3)	1.212	1.409
  μ / mm-1	7.536	9.863
  F(000)	2 988	4 664
  Total reflection	23 880	50 472
  Unique reflection	3 029	1 233
  Rint	0.189 7	0.104 0
  GOF	1.134	1.371
  Final R indices [I>2σ(I)]	R1=0.165 9, wR2=0.342 2	R1=0.149 6, wR2=0.292 7
  R indices (all data)	R1=0.213 0, wR2=0.366 4	R1=0.160 3, wR2=0.299 3
  aR1=∑||Fo|-|Fc||/∑|Fo|; bwR2=∑[w(Fo2-Fc2)2]/∑[w(Fo2)2]1/2.

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