Structure Of Zinc Complex Research Articles

Benzoate substituents effects on the structure of Zn(II) complexes and 1D 4,4′-bipyridine derived coordination polymers

The aim of this work is to study the influence of different substituents in two closely related ligands, 3,5-dihydroxybenzoate (3,5-(HO)2Bz) and 3,5-dimethoxybenzoate (3,5-(MeO)2Bz), in the structure of zinc complexes. The compound [Zn(3,5-(MeO)2Bz)2(CH3OH)]2 (2) has been synthesized, characterized and its crystal structure elucidated, showing a paddle wheel type dinuclear molecule, with four bridging carboxylate ligands in a syn-syn coordination mode and methanol molecules in the apical positions. This discrete structural array is different than the polymeric structure observed in {[Zn(µ-3,5-(HO)2Bz)(µ-OH2)(H2O)2]·3,5-(HO)2Bz·4H2O}n, previously reported in our group. These two zinc complexes were used as precursor for the synthesis of coordination polymers (CPs) with the 4,4′-bipyridine (4,4′-bpy) linker. The solvent used in their synthesis influences the chemical composition of this CPs. Thus, {[Zn(3,5-(HO)2Bz)2(µ-4,4′-bpy)]·2DMSO}n (3) was achieved in dimethylsulfoxide (DMSO) while {[Zn(3,5-(HO)2Bz)2(µ-4,4′-bpy)]·4,4′-bpy·1/2CH3OH}n (4) was formed in methanol (MeOH) as solvent. The reaction of 2 with 4,4′-bpy yielded [Zn2(μ-3,5-(MeO)2Bz)4(µ-4,4′-bpy)]n (5) in methanol, while after recrystallization in boiling water, complex {[Zn(3,5-(MeO)2Bz)2(µ-4,4′-bpy)]·H2O}n (6) was isolated in low yield. This compound 6 can also be synthesized by a mechanochemical approach, using water in a liquid assisted grinding. The crystal structures of complexes 3, 4 and 6 were elucidated, all three showing zigzag polymeric arrays. Both polymers containing 3,5-(MeO)2Bz (5 and 6), showed solid state luminescence.

Synthesis and Crystalline Structure of Zinc Complexes with Antihypertensive Drug Lisinopril

The structural investigation of Zn2+ complexes with the ligand lisinopril (LIS), an inhibitor of angiotensin-converting enzyme (ACE), was performed. The main objective is to compare if Zn-LIS coordination in vitro is similar to that observed in vivo. Two zinc complexes were obtained from different synthetic routes. The synthesis of LISZn1 used stirring, while for LISZn2 involved solvothermal conditions, which favoured the full deprotonation of lisinopril ligand. In this sense, the different synthetic routes resulted in the formation of complexes with notorious chemical and structural differences. The crystal structure of LISZn2 showed that the ligand is coordinated to Zn2+ ion by oxygen and nitrogen atoms which is different from that observed in vivo. In vitro, the coordination of lisinopril occurs only by an oxygen atom of the central carboxylate group. LISZn2 forms a one-dimensional (1D) coordination polymer and presents disorder atoms in its unit cell.

Synthesis, spectroscopic studies, X-ray powder diffraction data and biological activity of mixed transition metal complexes with oxalato and theophylline ligands

The new series of divalent metal complexes [M(ox)(thy)2]; M = Cd2+, Ni2+, Mn2+, Fe2+, Cu2+ and Zn2+, with mixed ligands oxalato (ox) and theophylline (thy) were prepared and characterized by molar conductance, FT-IR, UV–visible, 1H and 13C NMR and X-ray structure analysis. The crystal structure including the positions of the Zn (II) complex was determined by powder diffraction analysis using the FOX program. In the structure of zinc complex, the zinc (II) cations are octahedrally coordinated by two terminals N-bonding for theophylline ligand and by the O atoms of two oxalato bidentate ligand, resulting in discrete and slightly distorted octahedral complex. This complex was crystallized in the monoclinic system (C1 2/c1) space group and the unit cell parameters are a = 11.8364(1)Å, b = 4.5200(1)Å, c = 9.9942(1)Å with β (°) = 126.4770(2)°. The antimicrobial activity of the complexes was studied and the results of their tests show that the metal (II) complexes are more effective against several of bacterial and fungal strains.

Preparation and structure of zinc complexes containing pincer ligands and their application for Knoevenagel condensation in water

Two zinc complexes with Pybox ligands, 2,6-bis[4′,4′-dimethyloxazolin-2′-yl]pyridine (Dm-pybox) (1a) and 2,6-bis[4′-isopropyloxazolin-2′-yl]pyridine (i-Pr-pybox) (1b), have been synthesized and characterized. Reactions of zinc chloride with the pyridine-based pincer ligands result in formation of (Dm-Pybox)ZnCl2 (2a) and (i-Pr-Pybox)ZnCl2 (2b), respectively. Both complexes have been characterized by elemental analysis, NMR and IR spectra. The molecular structures of 2a and 2b have been determined by X-ray crystallography. Complex 2b is efficient in catalyzing Knoevenagel condensation of ferrocenecarboxaldehyde with activated methylene compounds in water.

Synthesis, Structure of Zinc Complexes Containing Sulfonylated Binaphtholate Ligands and Their Catalytic Activities towards Ring‐Opening Polymerization of Lactide and ε‐Caprolactone

AbstractReaction of sulfonylated binaphthol [2‐hydroxy‐2′‐tosyloxy‐1,1‐binaphthyl (1a, Ts‐Binol) or 2‐hydroxy‐2′‐(phenylsulfonyloxy)‐1,1‐binaphthyl (1b, Ps‐Binol)] with 1 equiv. of ZnEt2 afforded zinc complexes [(Ts‐Binol)ZnEt]2 (2a) and [(Ps‐Binol)ZnEt]2 (2b). Further reaction of zinc complexes 2a and 2b with benzyl alcohol (BnOH) gave the zinc benzyloxide [(Ts‐Binol)2Zn2(OBn)2]2 (3a) and [(Ps‐Binol)2Zn2(OBn)2]2 (3b). Alternatively, the zinc benzyloxides 3a and 3b could also be obtained by reaction of compound 1a or 1b with Zn(OBn)2 (in situ reaction of ZnEt2 and BnOH). The complexes were fully characterized by elemental analyses and spectroscopic analyses, and complexes 2a, 2b and 3a were further characterized by single‐crystal X‐ray analyses. The catalytic activities of these zinc complexes towards ring‐opening polymerization of ε‐caprolactone and D,L‐lactide were studied.

Synthesis and structures of zinc complexes with new binucleating ligands containing alkoxide bridges, and their activities in the hydrolysis of tris( p-nitrophenyl)phosphate

Four new binucleating ligands featuring a hydroxytrimethylene linker between two coordination sites (1,3-bis{ N-[3-(dimethylamino)propyl]- N-methylamino}propan-2-ol, HL 1 ; 1,3-bis{ N-[2-(dimethylamino)ethyl]- N-methylamino}propan-2-ol, HL 2 ; 1,3-bis[bis(2-methoxyethyl)amino]propan-2-ol, HL 3 ; and 1-bis[(2-methoxyethyl)amino]-3-{ N-[2-(dimethylamino)ethyl]- N-methylamino}propan-2-ol, HL 4 ) were synthesized, along with the corresponding zinc complexes. The structures of three dinuclear zinc complexes ([Zn 2 L 1 (μ-CH 3COO) 2]BPh 4 ( 1), [Zn 2 L 3 (μ-CH 3COO) 2]BPh 4 ( 3), and [Zn 2 L 4 (μ-CH 3COO)(CH 3COO)(EtOH)]BPh 4 ( 4)) and a tetranuclear zinc complex ({[Zn 2 L 2 (μ-CH 3COO)] 2(μ-OH) 2}(BPh 4) 2 ( 2)) were revealed by X-ray crystallography. Hydrolysis of tris( p-nitrophenyl)phosphate (TNP) by these zinc complexes in an acetonitrile solution containing 5% Tris buffer (pH 8.0) at 30 °C was investigated spectrophotometrically and by 31P NMR. Although zinc complexes 1, 3, and 4 did not show hydrolysis activity, the tetranuclear zinc complex 2, containing μ-hydroxo bridges, was capable of hydrolyzing TNP. This suggests that the hydroxide moiety in the complex may have an important role in the hydrolysis reaction.

Syntheses, spectroscopies and structures of zinc complexes with malate

Reactions of zinc(II) ion with racemic malic acid (C 4H 6O 5 = H 3mal) result in the isolation of four new zinc(II) malato complexes: (NH 4)[Zn( R-H 2mal) 3] · H 2O ( 1), trans-[Zn( R-H 2mal)( S-H 2mal)(H 2O) 2] · 2H 2O ( 2), (NH 4) 2[Zn( R-Hmal)( S-Hmal)] · 2H 2O ( 3), and [Zn 2( R-Hmal)( S-Hmal)(H 2O) 4] n · 2 nH 2O ( 4). Three R-malic acids in 1 act as bidentate ligands via their alcoholic and the central carboxy groups with Zn(II) ion, leaving the terminal carboxylic acid groups free. The R- and S-malates of 2 coordinate in a bidentate manner with zinc ion in trans-form. In 3, Zn(II) ion is coordinated by R- and S-malates in a tridentate fashion via their alcoholic and two carboxy groups. Complex 4 forms a two-dimensional layered structure through the links of a new dimeric unit [Zn 2( R-Hmal)( S-Hmal)(H 2O) 4] with one of the oxygen atoms from the terminal carboxy group of malate ligand. The coordination of malates depends on pH variation, on Zn:malate ratio, and also on temperature. Tridentate chelation of malate in 3 is found between pH 4.5–9.0. The soluble monomeric species 1– 3 have been investigated using 13C NMR spectra by long-time acquisition. The solution NMR spectra indicate that zinc malate complexes dissociate in H 2O (D 2O). Obvious downfield shifts of the central carboxy carbon atoms in 1– 3 are observed compared with those of free malate, which indicate that these zinc malate complexes dissociate in aqueous solution.

Fabrication and Characterization of Organic Light-Emitting Diodes Using Zinc Complexes as Hole-Blocking Layer

2-(2-Hydroxyphenyl)benzoxazole (HPB) was employed as organic ligand and the corresponding zinc complexes (Zn(HPB)2 and Zn(HPB)q) were synthesized. And their EL properties were characterized. The structures of zinc complexes were determined with FT-NMR, FT-IR, UV-Vis, and XPS. The thermal stability showed up to about 300 degrees C under nitrogen flow, which was measured by TGA. The photoluminescence (PL) of zinc complexes were measured from the DMF solution. The PL emitted in blue and yellow region, respectively. The EL devices were fabricated by the vacuum deposition. Two kinds of OLEDs devices were fabricated; ITO/NPB (40 nm)/Zn complexes (60 nm)/LiF/Al and ITO/NPB (40 nm)/Alq3 (60 nm)/Zn complexes (5 nm)/LiF/Al. Both of the EL properties as the emitting and the hole-blocking layer were investigated. The EL emission of Zn(HPB)q exhibited green light centered at 532 nm. The device showed a turn-on voltage at 5 V and a luminance of 6073 cd/m2 at 10 V. Meanwhile, the maximum EL the emission of the Zn(HPB)2 device was found to be at 447 nm. And the device showed a luminance of 2813 cd/m2 at 10 V. The ITO/NPB (40 nm)/Alq3 (60 nm)/Zn(HPB)2 (5 nm)/LiF/Al device showed increased luminance of L=17000 cd/m2 compared to L=12000 cd/m2 for similar device fabricated without the hole-blocking layer. And the turn-on voltage was significantly affected by the existence of the hole-blocking layer.