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A new mononuclear Cu(II) complex of 4-aminopyridine (4AP), [Cu(4AP)4]Cl2·2CH3OH ( 1 ), was obtained and structurally characterized by single-crystal X-ray diffraction methods. The complex is square-planar involving four monodentate 4AP molecules coordinated through the Npy atoms. A solid-state linear-dichroic spectroscopic analysis (IR-LD) as a suspension in a nematic liquid crystal was carried out over the 4000–400?cm -1 range and determined stereochemical parameters compared crystallographic data. Detailed IR characteristics are reported. [ABSTRACT FROM AUTHOR]

Abstract: Two mononuclear Cu(II) complexes, [Cu(L1H2)](ClO4)1.25Cl0.75·1.25H2O (1) and [Cu(L2H2)](ClO4)2 (2), of the pyridoxal Schiff base ligands N,N′-dipyridoxylethylenediimine (L1H2) and N,N′-dipyridoxyl-1,3-propanediimine (L2H2) are reported. X-ray crystal structures of both complexes are also reported. In both complexes the pyridoxal nitrogen atoms remain protonated. In the solid state, the tetradentate Schiff base ligand is virtually planar in 1, while in 2 the ligand conformation is like an inverted umbrella. In cyclic voltammetry experiments it is found that in these complexes the Cu(III) and Cu(I) states are more easily accessible than in their salen type analogs. The pyridoxal Schiff base complexes are also found to be resistant to oxidative electro-polymerization, unlike their corresponding salicyl aldehyde Schiff base complexes. [Copyright &y& Elsevier]

Abstract: This work describes the synthesis and X-ray crystallographic characterization of three nickel(II) complexes [Ni(3,2,3-tet){Ag(CN)2}2] (1), [Ni(3,2,3-tet)(μ-tp)] n ·1.5nH2O (2) and {[Ni(3,2,3-tet)(μ1,5-dca)](ClO4)} n (3) where 3,2,3-tet= N,N′-bis(3-aminopropyl)-1,2-ethylenediamine, tp=terephthalate and dca=dicyanamide. Compound 1 is a heterotrinuclear discrete distorted octahedral molecule whereas compound 2 forms a 1D polymeric network and an extended 2D network is formed by intermolecular hydrogen bonding. Interestingly, two adjacent 1D chains execute a novel double-helical network constructed by Ni(II) and the bridging dca ligand in compound 3. The variable temperature magnetic susceptibility measurements for compounds 2 and 3 were also carried out. [Copyright &y& Elsevier]

Anions and cations of the title compound, C5H8N3+·C4HO4−, are connected by moderately strong intermolecular N—H...O hydrogen bonds into an infinite three-dimensional network. Hydrogen squarate anions form dimers through strong O—H...O interactions. [ABSTRACT FROM AUTHOR]