Synthesis, spectroscopy, thermodynamics and structure of [ZnCl₂ (η³-dpktch)] (η³-dpktch = N,N,O- di-2-pyridyl ketone thiophene-2-carboxylic acid hydrazone)

Abstract

When dpktch was reacted with ZnCl 2 in refluxing acetonitrile in air [ZnCl 2 ( 3 -dpktch)] was isolated in good yield. Infrared spectra suggest weaker binding of dpktch in [ZnCl 2 ( 3 -dpktch)] than in [CdCl 2 ( 3 -dpktch)]. 1 H-NMR studies in non-aqueous media show that [ZnCl 2 ( 3 -dpktch)] is sensitive to changes in its environment and exchanges its amide proton. Electronic absorption spectral measurements confirmed the sensitivity of [ZnCl 2 ( 3 -dpktch)] to changes in its surroundings and show inter-conversion between two intra-ligand-charge-transfer transitions (ILCT) at 330 AE 2 nm and 404 AE 2 associated with [ZnCl 2 ( 3 -dpktch)] and its conjugate base. Thermo-optical measurements in non-aqueous dmf and dmso show facile interconversion between [ZnCl 2 ( 3 -dpktch)] and its conjugate base, respectively. Also, it is shown that protonation of dmf by [ZnCl 2 ( 3 -dpktch)] is exothermic (standard enthalpy of protonation ÁH ¼ À40.7 AE 1.8 kJ mol À1 ), but endothermic for dmso (ÁH ¼ þ8.3 AE 1.5 kJ mol À1 ). Chemical stimuli in concentrations as low as 5.0 Â 10 À7 M can be detected and determined using [ZnCl 2 ( 3 -dpktch)] in non-aqueous media. X-ray crystallographic studies on a monoclinic, P2 1 /n single crystal of [ZnCl 2 ( 3 -dpktch)] confirmed the N,N,O-coordination of dpktch and revealed interdigitated units of [ZnCl 2 ( 3 -dpktch)] connected via a web of hydrogen bonds.

Correlating Structure and KA2 Catalytic Activity of ZnII Hydrazone Complexes

“…The ZnÀ L bond lengths (ZnÀ N Ar 2.1390(18) Å, ZnÀ S thiolate 2.3516 (6) and ZnÀ N imine 2.1231(18) Å) observed in 3 fit into the range of values 2.125(4)-2.227(3), 2.324(2)-2.431(6) and 2.03(2)-2.156(4) Å, respectively, observed for the five-coordinate Zn II complexes with related tridentate NNS hydrazone-based ligands. [26][27][28][39][40][41][42][43][44][45][46] The azido ligands are coordinated to the Zn II in the bent mode, with NÀ NÀ Zn angles of 115.62 (16) and 123.08(17)°.…”

“…[12] Com-plexes encompassing NNX tridentate carbazone ligands form different types of coordination geometries. The geometry of pentacoordinated zinc(II) can be distorted trigonal bipyramidal, [13][14][15][16][17][18][19] distorted square pyramidal, [20][21][22][23][24][25][26] or somewhere between trigonal bipyramidal and square pyramidal. [27][28][29] Similarly, binuclear zinc(II) complexes of coordination number five with two acetate bridging ligands, in which three coordination sites are occupied by the NNS donor set of atoms, can have a trigonal bipyramidal or square pyramidal geometry.…”

Synthesis, and molecular sensing behavior of fac-[Re(CO)3(κ2-N,N-dpksc)Cl], dpksc=di-2-pyridyl ketone semicarbazone

“…Electrochemical reactions of CO 2 with fac-[Re(CO) 3 (dpk)Cl] measured on non-aqueous solvents showed strong solvent dependence and revealed metal-based and ligandbased reactivity [30]. Spectroscopic measurements done on nonaqueous solutions of di-2-pyridyl ketone hydrazones and their metal complexes show high sensitivity of these compounds to changes in their surroundings [32][33][34][35][36][37]. Solid state structures of a variety of di-2-pyridyl ketone derivatives and their metal compounds show strong solvent dependence due to solvent complex interaction and the presence of extensive network of hydrogen bond [33][34][35][36][37].…”

“…In continuation of our efforts to explore the chemistry of di-2-pyridyl ketone derivatives, this report will describe the synthesis and physico-chemical properties of the first rhenium compound di-2-pyridyl ketone semicarbazone (see Scheme 1). In previous reports, we described the synthesis, spectroscopic, electrochemical, and solid state structures of a variety of metal compounds that contain di-2-pyridyl ketone derivatives [30][31][32][33][34][35][36][37]. Electrochemical reactions of CO 2 with fac-[Re(CO) 3 (dpk)Cl] measured on non-aqueous solvents showed strong solvent dependence and revealed metal-based and ligandbased reactivity [30].…”

Spectroscopic and electrochemical properties of group 12 acetates of di-2-pyridylketone thiophene-2-carboxylic acid hydrazone (dpktch-H) complexes. The structure of [Cd(η3-N,N,O-dpktch-H)2]

“…Hydrazones are widely used as sensitive analytical reagents for the detection and determination of trace amounts of metal ions in biological, industrial and environmental samples [20][21][22][23]. We have been interested in the chemistry of di-2-pyridyl ketone derivatives (see Scheme 1) and reported on the synthesis and characterization of a variety of di-2-pyridyl ketone hydrazones and their metal compounds [24][25][26][27][28][29]. Herein, we wish to report on the synthesis, spectroscopic and electrochemical properties of group 12 acetate compounds of di-2-pyridyl ketone thiophene-2-carboxylic acid hydrazone and compare the results with those of Group 12 metal chlorides [24].…”