English

• 1. INTRODUCTION

  Amides widely exist in nature. In organisms, amides of many metal enzymes participate in metal coordination to promote the deprotonation of amides^[1]. As a result, R-C(O)NH-R' is transformed into nitrogen anion [R-C(O)N^--R']. The deprotonated amide nitrogen atom becomes a good electron donor^[2]. This structural feature of amide compounds plays an important role in the study of coordination chemistry and mechanism of simulated life process. Hydrazides containing -C(O)-NH-NH₂ chain-end have primary amino groups, which not only increase the coordination atoms and coordination modes, but also condense with aldehydes, ketones to produce Schiff bases and metal complexes with biological activity and photoelectric properties^[3-5]. The carbohydrazide or thiocarbohydrazide, as a kind of dihydrazide compound, can condense with salicylaldehyde to produce one-and two-Schiff base compounds with 1, 5-symmetric and 1, 5-asymmetric bissalicylaldehyde carbohydrazide, and the amide chain is easier to deprotonate^[6-8]. Because the C=N double bond has cis-and trans-isomerism, the rotation of C–N and N–N bonds produces space conformational isomerism, and the conversion of amide chain [Ar-CH=N-NH-C=O(S)-NH-N=CH-Ar] ketone and enol forms. Therefore, bissalicylaldehyde carbohydrazide is a multi-site and multi-mode ligand^{[9, 10]}. It is of great significance to explore the coordination between ligands with metals, and to synthesize complexes with new structures and properties. In this paper, four ligands of bis(4-diethylamino, 5-bromosalicylaldehyde) carbohydrazide (H₄L¹, H₄L²) and bis(salicylaldehyde, 5-bromo-salicylaldehyde) thiocarbohydrazide (H₄L³, H₄L⁴) were prepared by the condensation reaction of salicylaldehyde, 4-diethylamino and 5-bromosalicylaldehyde with carbohydrazide and thiocarbohydrazide, respectively. Four bis(substituted salicylaldehyde) carbohydrazide dibutyltin complexes T1~T4 were synthesized by microwave-assisted solvothermal method. The fluorescence properties of T(2, 4)-DMF-H₂O system were studied, and the activities of ligands and their complexes T1~T4 on the growth of these plants, such as Portulaca oleracea L., Amaranthus spinosus L., Cassia tora L., Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee and Amaranthus tricolor L. were evaluated.

  2. EXPERIMENTAL

  2.1 Materials and instruments

  MicroSYNT Lab station for microwave assisted (Italy). The melting points were obtained on an X-4 microscopic melting point apparatus and uncorrected. ¹H and ¹³C NMR spectra were measured on a Bruker Avance 500 spectrometer (Switzerland) with CDCl₃ as solvent and TMS as an internal standard. IR spectra (4000~400 cm^-1 range, KBr discs) were recorded on a Shimadzu FTIR Prestige-21 spectrometer. Elemental analyses of C, H and N were performed with a Perkin-Elmer 2400 II elemental analyzer. Crystal structure was determined on a Bruker Smart Apex II CCD X-ray diffractometer (Germany). F-7000 Fluorescence Spectrometer (Shimadzu). MGC-HP intelligent artificial climate box (Shanghai Yiheng Scientific Instrument Co., Ltd.).

  All reagents were purchased from commercial supplies (Energy chemical reagent Co., Lid; grade: CP) without further purification. Ligands bis(4-diethylaminosalicylaldehyde) carbohydrazide (H₄L¹)^[11], bis(salicylaldehyde) thiocarbohydrazide (H₄L³)^[12], and bis(5-bromosalicylaldehyde) thiocarbohydrazide (H₄L⁴)^{[11, 13]} were synthesized in our laboratory and characterized by elemental analysis, IR and NMR.

  2.2 Preparation of ligand H₄L²

  According to reference^{[7, 11]}, a mixture of 5-bromosalicylaldehyde (40 mmol), carbohydrazide (20 mmol) and ethanol-acetic acid (30 mL, V/V = 7:3) was placed in a 100 mL reactor, then the mixture was stirred and heated to reflux for 6 hours. After cooling down to room temperature, the solution was filtered and the solvent was removed by vacuum evaporation. The crude product was recrystallized from appropriate solvent to yield bis(5-bromosalicylaldehyde) carbohydrazide (H₄L²), light yellow powder 6.755 g, yield: 74.1%, m.p.: 125~126 ℃. Anal. Calcd. (%) for C₁₅H₁₂Br₂N₄O₃: C, 39.50; H, 2.65; N, 12.28. Found (%): C, 39.49; H, 2.66; N, 12.27. IR (KBr): 3235 (m, ν_O-H), 3044 (m, ν_Ar-H, ν_N-H), 1682 (s, ν_C=O), 1622 (s, ν_C=N) cm^-1. ¹H NMR(DMSO-d₆, 500MHz) δ (ppm): 11.05 (s, 1H, -OH), 10.98 (s, 1H, -OH), 10.88 (s, 2H, -NH-), 9.01 (s, 1H, -CH=N), 8.94 (s, 1H, -CH=N), 6.85~8.50 (m, 6H, Ar-H).

  2.3 Syntheses of the complexes

  A mixture of 1 mmol ligand, 2 mmol dibutyltin oxide, and 15 mL anhydrous methanol was placed in a 50 mL Teflon-lined reactor. The reactants are stirred and the reactor is sealed, and set on the microwave power 800 W, 120 ℃ of MicroSYNT Lab station for microwave assisted synthesis. The mixture was heated by microwave radiation for two hours. The reactants were naturally cooled down to room temperature. Then the solution was obtained by filtration, and the filtrate was removed by evaporation in vacuo. Crystals of the complexes were obtained by recrystallization from methanol. The yield was calculated based on ligand.

  T1, brownish yellow crystal, 0.626 g. Yield: 69.4%, m.p.: 167~168 ℃. Anal. Calcd. (%) for C₃₉H₆₄N₆O₃Sn₂: C, 51.91; H, 7.15; N, 9.31. Found (%): C, 51.92; H, 7.15; N, 9.30. IR: 3019 (s, ν_Ar-H), 2922 (m, ν_C-H), 1620 (s, ν_C=N), 573 (m, ν_Sn-O), 538 (s, ν_Sn-O), 453 (s, ν_Sn-N), 432 (s, ν_Sn-C) cm^-1. ¹H NMR (CDCl₃) δ (ppm): 8.17 (s, 1H, -CH=N), 7.66 (s, 1H, -CH=N), 5.97~6.90 (m, 6H, Ar-H), 3.35~3.37 (m, 8H, -NCH₂-), 0.84~1.69 (m, 48H, -CH₂CH₃). ¹³C NMR (CDCl₃) δ (ppm): 166.74, 166.64, 165.22 (-C=N), 155.08, 152.24, 152.22, 147.32, 107.55, 106.84, 102.85, 102.77, 100.91, 100.56(Ar-C), 27.50, 27.35, 27.20, 26.89, 26.60, 26.51, 26.24, 22.34, 22.13(-CH₂-), 13.66, 13.59, 12.84, 12.81, 12.69 (-CH₃).

  T2, golden yellow crystal, 0.484 g. Yield: 70.5%, m.p.: 193~194 ℃. Anal. Calcd. (%) for C₉₃H₁₃₂Br₆N₁₂O₉Sn₆: C, 40.56; H, 4.83; N, 6.10. Found (%): C, 40.55; H, 4.87; N, 6.11. IR: 2918 (m, ν_Ar-H), 2851 (m, ν_C-H), 1599 (s, ν_C=N), 584 (s, ν_Sn-O), 546 (s, ν_Sn-O), 465 (s, ν_Sn-N), 448 (s, ν_Sn-C) cm^-1. ¹H NMR (CDCl₃) δ (ppm): 8.38 (s, 1H, -CH=N), 8.32 (s, 1H, -CH=N), 8.28 (s, 1H, -CH=N), 8.01 (s, 1H, -CH=N), 7.83 (s, 1H, -CH=N), 7.72 (s, 1H, -CH=N), 6.59~7.30 (m, 18H, Ar-H), 1.31~1.65 (m, 72H, -CH₂-), 0.84~0.87 (m, 36H, -CH₃). ¹³C NMR (CDCl₃) δ (ppm): 163.54, 162.59 (-C=N), 136.17, 135.93, 134.59, 133.91, 133.56, 133.36, 132.26, 123.46, 123.19, 122.89, 121.59, 118.94, 117.27(Ar-C), 27.29, 26.81, 26.78, 26.57, 26.49, 26.25, 22.84, 22.80, 22.72, 22.60, 22.55, 22.47(-CH₂-), 13.62, 13.59, 13.57(-CH₃).

  T3, yellow crystal, 0.416 g. Yield: 76.3%, m.p.: 215~216 ℃. Anal. Calcd. (%) for C₂₃H₃₀O₂N₄SSn: C, 50.66; H, 5.55; N, 10.27. Found (%): C, 50.67; H, 5.54; N, 10.27. IR: 3150 (m, ν_O-H), 3019 (m, ν_N-H), 2959 (m, ν_Ar-H), 2913 (m, ν_C-H), 1607 (s, ν_C=N), 540 (w, ν_Sn-O), 502 (w, ν_Sn-N), 475 (w, ν_Sn-C), 440 (w, ν_Sn-S) cm^-1. ¹H NMR (CDCl₃) δ (ppm): 11.13 (s, 1H, -OH), 8.72 (s, 1H, -CH=N), 8.59 (s, 1H, -CH=N), 7.90 (s, 1H, -N-H), 6.70~7.32 (m, 8H, Ar-H), 1.31~1.69 (m, 12H, -CH₂), 0.88 (t, 6H, -CH₃). ¹³C NMR (CDCl₃) δ (ppm): 166.97, 166.55, 164.71, 162.74, 159.75, 157.69 (-C=N), 143.73, 135.22, 133.89, 133.45, 132.56, 130.93, 129.95, 121.51, 119.75, 119.35, 117.94, 117.13, 117.17, 117.05, 116.81(Ar-C), 27.52, 27.39, 27.27, 26.52, 26.23(-CH₂-), 13.62(-CH₃).

  T4, brownish yellow crystal, 0.569 g. Yield: 80.9%, m.p.: 173~174 ℃. Anal. Calcd. (%) for C₂₃H₂₈Br₂N₄O₂SSn: C, 39.29; H, 4.01; N, 7.97. Found (%): C, 39.28; H, 4.02; N, 7.98. IR: 3140 (m, ν_O-H), 2955 (m, ν_N-H), 2924 (m, ν_Ar-H), 2874 (m, ν_C-H), 1589 (s, ν_C=N), 546 (w, ν_Sn-O), 469 (w, ν_Sn-N), 444 (w, ν_Sn-C), 413 (w, ν_Sn-S) cm^-1. ¹H NMR (CDCl₃) δ (ppm): 11.13 (s, 2H, -OH), 8.59 (s, 2H, -CH=N), 7.90 (s, 2H, -N-H), 6.70~7.32 (m, 12H, Ar-H), 1.32~1.69 (m, 24H, -CH₂), 0.88 (t, 12H, -CH₃). ¹³C NMR (CDCl₃) δ (ppm): 166.98, 165.92, 161.36, 156.65(-C=N), 142.19, 137.67, 135.11, 133.50, 131.95, 123.46, 119.58, 118.99, 118.20, 110.95, 108.02(Ar-C), 27.35, 27.23, 26.49, 26.41(-CH₂-), 13.61(-CH₃).

  2.4 Crystal structure determination of T2

  The crystal of T2 with dimensions of 0.13mm × 0.12mm × 0.10mm was selected. The crystal data were collected by a Bruker Smart Apex II CCD diffractometer (MoKα radiation, λ = 0.71073 Å) in the ranges of 1.96≤θ≤29.53º, –34≤h≤27, –14≤k≤22 and –36≤l≤36. A total of 29020 reflections were collected and 18877 were independent (R_int = 0.0323), of which 16160 observed reflections with I > 2σ(I) were used in the succeeding refinements. The structure was solved by direct methods with SHELXS program and refined by full-matrix least-squares technique using the SHELXL^[14]. Hydrogen atoms were placed in calculated positions or located from difference Fourier maps, and refined isotropically with isotropic vibration parameters related to the non-hydrogen atom to which they are bound. All calculations were performed with SHELXTL program. Empirical formula, C₉₃H₁₃₂Br₆N₁₂O₉Sn₆, 2753.71 g/mol, monoclinic system, space group Ia, a = 25.0359(11), b = 16.8398(6), c = 26.665(2) Å, β = 112.443(5)°, V = 10390.5(10) ų, T = 293(2) K, Z = 4, D_c = 1.760 Mg/m³, µ = 3.786 mm^–1 and F(000) = 5424. A full-matrix least-squares refinement gave the final R = 0.0415, wR = 0.1005 (w = 1/[σ²(F_o²) + (0.0630P)² + 0.0000P], where P = (F_o² + 2F_c²)/3), S = 1.036, (Δρ)_max = 1.414 and (Δρ)_min = –0.842 e/ų.

  2.5 Determination of herbicidal activity

  The herbicidal activities of the ligands and their complexes were evaluated by plating method^[7]. The root and stem lengths of the target plants, such as Portulaca oleracea L., Amaranthus spinosus L., Cassia tora L., Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee and Amaranthus tricolor L., were determined. Each treatment was repeated thrice and the growth inhibition rate (I) of target plants was calculated by comparing the difference between the average plant growth length (l₀) of water as a reference solution and the average plant growth length (l₁) of the treated plants compared with the l₀ value. If I is positive, the ligand or complex has inhibitory effect on target plants, while when I is negative, it can promote the target plants.

  $ I = \frac{{l0 - l1}}{{l0}} \times 100\% $

  3. RESULTS AND DISCUSSION

  Our previous research and comparison show that microwave irradiation method has the advantages of fast reaction, high yield, convenient operation and environmentfriendly. It is better than the conventional heating method^[15].

  3.1 Spectral characteristics

  The interaction between bis(salicylaldehyde) carbohydrazide or thiocarbohydrazide and metal may produce mononuclear and binuclear complexes. The characteristic spectra of hydroxyl group (O–H), carbonyl (> C=O) and metal coordinated Sn–N(O) are important information to distinguish their structural changes. For example, the H₄L¹ and H₄L² have absorption peak, with a strong, wide peak of hydroxyl ν_(O-H) at 3273, 3235 cm^-1, and a very strong peak of carbonyl ν_(C=O) at 1707 and 1682 cm^-1, respectively. But these characteristic peaks disappeared in T1 and T2, and the strong characteristic absorption peaks of ν_(C=N) were weakened obviously. Also, in the low field of ¹H NMR spectra, the proton peaks of phenolic hydroxyl group (O–H) and amide (> N-H) disappeared, and weak characteristic peaks of ν_(Sn-O), ν_(Sn-N) and ν_(Sn-C) appeared in the infrared spectra of the complexes^{[16, 17]}. These changes of spectral characteristics support each other, indicating binuclear complexes T1 and T2. The characteristic peaks of thiocarbonyl (> C=S) at 1272 (H₄L³) and 1277 cm^-1 (H₄L⁴) disappear in T3 and T4, respectively, and the absorption peaks of ν_(C=N) are weakened. However, the moderate and wide infrared characteristic absorption peaks of ν_(O-H) and the proton peaks of low-field phenol hydroxyl (O–H) and amino (> N–H) did not disappear, and weak characteristic peaks of ν_(Sn-O), ν_(Sn-N) and ν_(Sn-C) were produced^[15], and ν_(Sn-S) weak peaks were also produced in T3 and T4^[18], which indicated that the mononuclear complexes T3 and T4 were formed by the coordination of ligands with tin. These ¹³C NMR data of the complexes further support the structures.

  3.2 Crystal structure of T2

  Bis(brominated salicylaldehyde) carbohydrazides have seven atoms of nitrogen and oxygen, which may coordinate with metal. The hydrogen on amide nitrogen is transferred to oxygen of carbonyl > C=O, resulting in the conversion of ketone form to enol^{[16, 19]}, and the enolation form conjugated with C=N, aromatic rings. X-ray diffraction analysis shows that a phenoxy, imine N and dehydrogenated nitrogen of the bis(brominated salicylaldehyde) carbohydrazide coordinate with dibutyltin to form one unit, (Bu₂Sn)₂L. The bond lengths and bond angles between the tin atom and ligand are different. Five-coordinated distorted triangular bipyramids and six-coordinated distorted octahedral configurations are formed in a unit structure, respectively. Interestingly, the nitrogen atom which is dehydrogenated from one unit interacts with the tin atom of another unit to form a trimer complex, [(Bu₂Sn)₂L]₃. The three six-coordinated tin atoms Sn(2), Sn(4) and Sn(6) are located in the core to form a small triangle. Three five-coordinated tin atoms Sn(1), Sn(3) and Sn(5) form a large triangle at the outer. The small triangle is inverted in the large triangle to form a spatial skeleton structure. The plane angle of the two triangles is 0.00°, and six tin atoms are coplanar. The plane of six benzene rings is obviously deviated from the plane of these tin atoms, forming a "propeller" like structure. The crystal molecular structure of the complex is shown in Fig. 1, and its bond parameters are shown in Table 1.

  Figure 1

  

  Figure 1.  Molecular structure of T2 (butyls and H atoms are omitted for clarity)

  DownLoad: Full-Size Img PowerPoint

  Table 1

  

  Table 1.  Selected Bond Lengths (Å) and Bond Angles (°) of T2

  DownLoad: CSV

  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Sn(1)–O(1)	2.084(6)		Sn(3)–N(7)	2.231(7)		Sn(6)–O(8)	2.291(6)
  Sn(1)–N(1)	2.182(7)		Sn(4)–O(5)	2.081(6)		Sn(6)–N(12)	2.359(7)
  Sn(1)–N(3)	2.219(7)		Sn(4)–O(6)	2.317(6)		Sn(6)–N(2)	2.486(7)
  Sn(2)–O(2)	2.086(6)		Sn(4)–N(8)	2.387(7)		N(1)–N(2)	1.374(10)
  Sn(2)–O(3)	2.337(6)		Sn(4)–N(10)	2.453(7)		N(3)–N(4)	1.410(9)
  Sn(2)–N(4)	2.370(7)		Sn(5)–O(7)	2.076(6)		N(5)–N(6)	1.394(9)
  Sn(2)–N(6)	2.451(7)		Sn(5)–N(9)	2.176(7)		N(7)–N(8)	1.355(10)
  Sn(3)–O(4)	2.089(6)		Sn(5)–N(11)	2.227(7)		N(9)–N(10)	1.372(10)
  Sn(3)–N(5)	2.191(7)		Sn(6)–O(9)	2.087(6)		N(11)–N(12)	1.373(10)
  Angle	(°)		Angle	(°)		Angle	(°)
  O(1)–Sn(1)–N(1)	84.3(2)		C(24)–Sn(2)–N(6)	87.6(4)		O(7)–Sn(5)–N(9)	83.1(3)
  C(20)–Sn(1)–N(1)	113.3(3)		O(3)–Sn(2)–N(6)	132.9(2)		O(7)–Sn(5)–N(11)	153.6(3)
  C(16)–Sn(1)–N(1)	121.1(3)		N(4)–Sn(2)–N(6)	157.4(2)		N(9)–Sn(5)–N(11)	71.4(3)
  O(1)–Sn(1)–N(3)	155.4(2)		O(4)–Sn(3)–N(5)	82.9(2)		O(9)–Sn(6)–O(8)	145.7(2)
  C(20)–Sn(1)–N(3)	97.3(3)		O(4)–Sn(3)–N(7)	150.6(2)		O(9)–Sn(6)–N(12)	77.9(2)
  C(16)–Sn(1)–N(3)	100.5(3)		N(5)–Sn(3)–N(7)	71.4(3)		O(8)–Sn(6)–N(12)	68.3(2)
  N(1)–Sn(1)–N(3)	71.1(3)		O(5)–Sn(4)–O(6)	145.7(2)		C(86)–Sn(6)–N(2)	81.3(4)
  O(2)–Sn(2)–O(3)	145.9(2)		O(5)–Sn(4)–N(8)	78.0(2)		O(9)–Sn(6)–N(2)	81.9(2)
  O(2)–Sn(2)–N(4)	78.2(2)		O(6)–Sn(4)–N(8)	68.2(2)		O(8)–Sn(6)–N(2)	132.2(2)
  O(3)–Sn(2)–N(4)	68.8(2)		O(5)–Sn(4)–N(10)	82.1(2)		N(12)–Sn(6)–N(2)	159.5(2)
  O(2)–Sn(2)–N(6)	80.9(2)		O(6)–Sn(4)–N(10)	132.1(2)
  C(28)–Sn(2)–N(6)	86.6(4)		N(8)–Sn(4)–N(10)	159.3(2)

  3.3 Fluorescence properties of T(2, 4)-DMF-H₂O system

  It has been found that some organic small molecules, in good solvent, compound displayed very weak fluorescence, while strong emission was observed when they were placed in poor solvent. The solution produces an enhanced aggregation fluorescence (AEE) effect^{[20, 21]}. We also found this luminescence phenomenon in DMF solution of organotin complex^[22]. In order to search for luminescent materials, T2 and T4-DMF-H₂O (V: V) solutions with concentration of 0.363 (T2) and 1.422 (T4) μM·L^-1 were prepared respectively. The UV-Vis absorption spectra of T(2, 4)-DMF-H₂O solution were measured when the volume ratio of DMF to water was 7:2. The fluorescence emission spectra of T(2, 4)-DMF-H₂O with different water volume fractions (WVF) were measured by fluorescence spectrometer, and the influence of water on the fluorescence intensity of solution system was explored. The results are shown in Fig. 2. There is a fluorescence emission peak at 402 nm in DMF solution of T2. When a certain amount of water is added into T2-DMF solution, the fluorescence intensity almost linearly decreases with the increase of WVF. When the water content reaches 90%, there is almost no fluorescence. However, when carbohydrazide was replaced by thiocarbohydrazide, the fluorescence intensity of the complex T4-DMF-H₂O solution increases with the increase of WVF, and gets to the maximum when the WVF reaches 20%, which indicates that the T4-DMF-H₂O system has the aggregation fluorescence enhancement effect at the WVF of 0~20%^[20]. Then, with the increase of WVF, the fluorescence intensity decreases, and finally fluorescence quenching occurs. Maybe due to the increase of water content, the solution system is unstable, thus resulting in the loss of aggregation fluorescence enhancement effect, which provides a reference for further research on the aggregationinduced fluorescence materials of complexes.

  Figure 2

  

  Figure 2.  Fluorescence spectra of T2 and T4 in DMF-H₂O with different WVF

  (Inset shows a plot of maximum fluorescence intensity of complex in DMF-H₂O mixtures with different WVF)

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  3.4 Herbicidal activity

  The effects of ligands (H₄L) and their complexes (T) on the growth of roots (R) and stems (S) of five target plants, such as, Portulaca oleracea L., Amaranthus spinosus L., Cassia tora L., Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee and Amaranthus tricolor L. were investigated. As shown in Table 2, the bioactivity of organotin compounds is related to the groups and ligands attached to tin. It can be seen from Table 2 that, except H₄L¹ and T1, H₄L² and T2 which have few effects on Amaranthus spinosus L. and Brassica campestris L.ssp. chinensis var. utilis Tsen et Lee respectively, the ligands and their complexes have effects on the growth of target plants^[12]. However, in the concentration range of the test solution, most of the ligands (except H₄L¹ which has a greater effect on Cassia tora L.) have less effects. For the same target plant, the complex has a greater growth inhibition than its ligand. With the increase of concentration, the effect of the complexes on target plants increased^{[12, 16]}. When the concentration of the test solution was 100 mg/L, the inhibition rate (I) of most target plants was almost 100%. The inhibition rate of T1 on the root growth of Amaranthus spinosus L. was 28% at the test concentration of 50 mg/L. When one butyl of T1 was replaced by chlorine atom, the inhibition rate on the root growth of Amaranthus spinosus L. was 70%. If the carbonyl oxygen of ligand was replaced by sulfur atom and one butyl was substituted by chlorine atom, the inhibition rate on the root growth of Amaranthus spinosus L. was 100%^[11].

  Table 2

  

  Table 2.  Inhibition Rate (I%) of Ligand (H₄L) and Its Complex (T) on Plant Roots (R) and Stem (S)

  DownLoad: CSV

  	Po		As		Bc		At		Ct
  	R	S	R	S	R	R	S	R	S	R
  c(mg/L)	H4L1/T1
  10	14/12	12/14	11/12	10/16	24/11	22/17	14/16	22/21	14/42	12/44
  25	24/24	22/22	23/26	15/23	54/28	42/30	24/29	32/32	23/74	22/72
  50	35/23	23/36	27/28	18/39	85/36	85/38	25/33	33/39	35/100	23/100
  100	37/46	35/68	32/53	22/58	100/100	100/100	30/100	37/100	37/100	35/100
  150	42/88	41/89	37/44	27/55	100/100	100/100	40/100	40/100	42/100	41/100
  200	39/100	36/100	39/56	30/62	100/100	100/100	37/100	40/100	39/100	36/100
  c(mg/L)	H4L2/T2
  10	8/28	7/36	10/37	12/33	9/45	8/26	5/10	7/14	10/33	11/35
  25	10/58	12/53	11/79	13/66	11/64	10/54	6/12	11/22	14/64	12/66
  50	13/77	15/76	17/98	15/89	11/87	18/89	11/22	13/26	16/79	15/82
  100	15/97	13/99	19/100	16/97	13/99	25/98	14/24	14/28	18/96	16/97
  150	16/100	15/100	22/100	15/100	15/100	30/100	17/35	16/39	19/100	15/100
  200	16/100	16/100	24/100	17/100	17/100	32/100	22/37	15/44	20/100	17/100
  c(mg/L)	H4L3/T3
  10	16/38	16/37	31/46	32/46	24/60	24/61	–15/–30	–16/–30	17/54	16/55
  25	32/79	32/81	35/76	36/76	45/85	45/85	–33/–47	–34/–49	24/87	24/90
  50	44/98	44/99	46/88	45/89	55/98	55/97	–45/–69	–34/–71	33/99	34/100
  100	45/100	47/100	56/98	57/100	67/100	67/100	–60/–60	–59/–59	46/100	46/100
  150	52/100	52/100	64/100	64/100	70/100	70/100	–62/–60	–64/–60	58/100	59/100
  200	56/100	56/100	67/100	67/100	72/100	72/100	–63/–57	–63/–60	58/100	59/100
  c(mg/L)	H4L4/T4
  10	2/33	–1/35	–24/–31	–15/–38	2/43	12/36	2/33	0/36	2/24	–1/26
  25	5/77	5/86	–13/–47	–8/–36	3/77	11/86	0/46	0/87	5/57	5/52
  50	3/100	6/100	–7/–44	–4/–40	4/100	14/100	1/77	0/80	3/78	6/80
  100	3/100	5/100	13/–56	15/–57	10/100	10/100	0/97	2/100	3/100	5/100
  150	4/100	2/100	45/–38	46/–46	13/100	10/100	4/100	2/100	4/100	2/100
  200	10/100	7/100	67/–45	57/–60	17/100	15/100	3/100	2/100	10/100	7/100
  Note: the abbreviations of symbols are: R plant roots, S plant stems; Po Portulaca oleracea L., As Amaranthus spinosus L., Ct Cassia tora L., Bc Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee and At Amaranthus tricolor L

  It is significant that H₄L³, T3 and H₄L⁴, T4 have negative inhibition rate (I) on the growth of Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee and Amaranthus spinosus L. respectively, and promote the growth of Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee and Amaranthus spinosus L.. It is possible that the sulfurcontaining organic compounds have special effects on the growth of Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee and Amaranthus spinosus L.. Therefore, the title complexes T1~T4 have broad activities on the growth of target plants, and can be used as candidate herbicides for further study.

  4. CONCLUSION

  A series of bis(substituted salicylaldehyde) carbohydrazide dibutyltin complexes were synthesized by the reaction of dibutyltin oxide with bis(substituted salicylaldehyde) carbohydrazide or thiocarbohydrazide in the microwave methanol solvothermal method. Complexes T2 and T4 have good fluorescence properties in DMF-H₂O solution system. When the water volume fraction of T4-DMF-H₂O system is 0~20%, it has the effect of aggregation fluorescence enhancement. The complexes have good activity on five target plants of Portulaca oleracea L., Amaranthus spinosus L., Cassia tora L., Brassica campestris L.ssp.chinensis var.utilis Tsen et Lee and Amaranthus tricolor L. These complexes can be used as candidate compounds of herbicides for further study.

  
  
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• 

  Figure 1  Molecular structure of T2 (butyls and H atoms are omitted for clarity)

  下载: 全尺寸图片 幻灯片
  

  Figure 2  Fluorescence spectra of T2 and T4 in DMF-H₂O with different WVF

  (Inset shows a plot of maximum fluorescence intensity of complex in DMF-H₂O mixtures with different WVF)

  下载: 全尺寸图片 幻灯片

  Table 1.  Selected Bond Lengths (Å) and Bond Angles (°) of T2

  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Sn(1)–O(1)	2.084(6)		Sn(3)–N(7)	2.231(7)		Sn(6)–O(8)	2.291(6)
  Sn(1)–N(1)	2.182(7)		Sn(4)–O(5)	2.081(6)		Sn(6)–N(12)	2.359(7)
  Sn(1)–N(3)	2.219(7)		Sn(4)–O(6)	2.317(6)		Sn(6)–N(2)	2.486(7)
  Sn(2)–O(2)	2.086(6)		Sn(4)–N(8)	2.387(7)		N(1)–N(2)	1.374(10)
  Sn(2)–O(3)	2.337(6)		Sn(4)–N(10)	2.453(7)		N(3)–N(4)	1.410(9)
  Sn(2)–N(4)	2.370(7)		Sn(5)–O(7)	2.076(6)		N(5)–N(6)	1.394(9)
  Sn(2)–N(6)	2.451(7)		Sn(5)–N(9)	2.176(7)		N(7)–N(8)	1.355(10)
  Sn(3)–O(4)	2.089(6)		Sn(5)–N(11)	2.227(7)		N(9)–N(10)	1.372(10)
  Sn(3)–N(5)	2.191(7)		Sn(6)–O(9)	2.087(6)		N(11)–N(12)	1.373(10)
  Angle	(°)		Angle	(°)		Angle	(°)
  O(1)–Sn(1)–N(1)	84.3(2)		C(24)–Sn(2)–N(6)	87.6(4)		O(7)–Sn(5)–N(9)	83.1(3)
  C(20)–Sn(1)–N(1)	113.3(3)		O(3)–Sn(2)–N(6)	132.9(2)		O(7)–Sn(5)–N(11)	153.6(3)
  C(16)–Sn(1)–N(1)	121.1(3)		N(4)–Sn(2)–N(6)	157.4(2)		N(9)–Sn(5)–N(11)	71.4(3)
  O(1)–Sn(1)–N(3)	155.4(2)		O(4)–Sn(3)–N(5)	82.9(2)		O(9)–Sn(6)–O(8)	145.7(2)
  C(20)–Sn(1)–N(3)	97.3(3)		O(4)–Sn(3)–N(7)	150.6(2)		O(9)–Sn(6)–N(12)	77.9(2)
  C(16)–Sn(1)–N(3)	100.5(3)		N(5)–Sn(3)–N(7)	71.4(3)		O(8)–Sn(6)–N(12)	68.3(2)
  N(1)–Sn(1)–N(3)	71.1(3)		O(5)–Sn(4)–O(6)	145.7(2)		C(86)–Sn(6)–N(2)	81.3(4)
  O(2)–Sn(2)–O(3)	145.9(2)		O(5)–Sn(4)–N(8)	78.0(2)		O(9)–Sn(6)–N(2)	81.9(2)
  O(2)–Sn(2)–N(4)	78.2(2)		O(6)–Sn(4)–N(8)	68.2(2)		O(8)–Sn(6)–N(2)	132.2(2)
  O(3)–Sn(2)–N(4)	68.8(2)		O(5)–Sn(4)–N(10)	82.1(2)		N(12)–Sn(6)–N(2)	159.5(2)
  O(2)–Sn(2)–N(6)	80.9(2)		O(6)–Sn(4)–N(10)	132.1(2)
  C(28)–Sn(2)–N(6)	86.6(4)		N(8)–Sn(4)–N(10)	159.3(2)

  下载: 导出CSV

  Table 2.  Inhibition Rate (I%) of Ligand (H₄L) and Its Complex (T) on Plant Roots (R) and Stem (S)

  	Po		As		Bc		At		Ct
  	R	S	R	S	R	R	S	R	S	R
  c(mg/L)	H4L1/T1
  10	14/12	12/14	11/12	10/16	24/11	22/17	14/16	22/21	14/42	12/44
  25	24/24	22/22	23/26	15/23	54/28	42/30	24/29	32/32	23/74	22/72
  50	35/23	23/36	27/28	18/39	85/36	85/38	25/33	33/39	35/100	23/100
  100	37/46	35/68	32/53	22/58	100/100	100/100	30/100	37/100	37/100	35/100
  150	42/88	41/89	37/44	27/55	100/100	100/100	40/100	40/100	42/100	41/100
  200	39/100	36/100	39/56	30/62	100/100	100/100	37/100	40/100	39/100	36/100
  c(mg/L)	H4L2/T2
  10	8/28	7/36	10/37	12/33	9/45	8/26	5/10	7/14	10/33	11/35
  25	10/58	12/53	11/79	13/66	11/64	10/54	6/12	11/22	14/64	12/66
  50	13/77	15/76	17/98	15/89	11/87	18/89	11/22	13/26	16/79	15/82
  100	15/97	13/99	19/100	16/97	13/99	25/98	14/24	14/28	18/96	16/97
  150	16/100	15/100	22/100	15/100	15/100	30/100	17/35	16/39	19/100	15/100
  200	16/100	16/100	24/100	17/100	17/100	32/100	22/37	15/44	20/100	17/100
  c(mg/L)	H4L3/T3
  10	16/38	16/37	31/46	32/46	24/60	24/61	–15/–30	–16/–30	17/54	16/55
  25	32/79	32/81	35/76	36/76	45/85	45/85	–33/–47	–34/–49	24/87	24/90
  50	44/98	44/99	46/88	45/89	55/98	55/97	–45/–69	–34/–71	33/99	34/100
  100	45/100	47/100	56/98	57/100	67/100	67/100	–60/–60	–59/–59	46/100	46/100
  150	52/100	52/100	64/100	64/100	70/100	70/100	–62/–60	–64/–60	58/100	59/100
  200	56/100	56/100	67/100	67/100	72/100	72/100	–63/–57	–63/–60	58/100	59/100
  c(mg/L)	H4L4/T4
  10	2/33	–1/35	–24/–31	–15/–38	2/43	12/36	2/33	0/36	2/24	–1/26
  25	5/77	5/86	–13/–47	–8/–36	3/77	11/86	0/46	0/87	5/57	5/52
  50	3/100	6/100	–7/–44	–4/–40	4/100	14/100	1/77	0/80	3/78	6/80
  100	3/100	5/100	13/–56	15/–57	10/100	10/100	0/97	2/100	3/100	5/100
  150	4/100	2/100	45/–38	46/–46	13/100	10/100	4/100	2/100	4/100	2/100
  200	10/100	7/100	67/–45	57/–60	17/100	15/100	3/100	2/100	10/100	7/100
  Note: the abbreviations of symbols are: R plant roots, S plant stems; Po Portulaca oleracea L., As Amaranthus spinosus L., Ct Cassia tora L., Bc Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee and At Amaranthus tricolor L

  下载: 导出CSV
•