Imidazole-imidazole stacking in some inorganic complexes

Reaction of CuCl2 center dot 2H(2)O with the 1:1 condensate (L) of 2-(2-aminoethyl) pyridine and 1-methyl-2-imidazolecarboxaldehyde in methanol yields monomeric CuLCl2 center dot H2O (1). Recrystallisation of 1 from aqueous methanol medium containing excess of PF6- affords the 1D coordination polymer [CuLCl](n)(PF6)(n) (2). A chloride bridge results in the coordination polymer. A face-to-face interaction is observed between the imidazole rings in 2. The interaction influences the structure and magnetic properties of 2 markedly. The complex 2 is ferromagnetic with a J value of 1.79 +/- 0.01 cm (1). The imidazole fragments in 2 are coordinated to the metal. In mononuclear [HgL2 ''](ClO4)(2), where L '' is the 1:2 condensate of ethylenediamine and 1-methyl-2-imidazolecarboxaldehyde, the imidazolyl moieties are not under the direct influence of the metal. Here the imidazole-imidazole interaction is angular and more distant. (C) 2009 Elsevier B.V. All rights reserved.

Effect of an ancillary ligand on single helix-double helix interconversion in copper complexes. Copper(I)-water bond

Reaction of Cu(ClO(4))(2)center dot 6H(2)O with the 1:2 condensate of benzildihydrazone and 2-acetylpyridine, in methanol in equimolar ratio yields a green compound which upon recrystallisation from 1:1 CH(2)Cl(2)-C(6)H(6) mixture affords [CuL(H(2)O)](ClO(4))(2)center dot 1/2C(6)H(6). The complex crystallises in the space group P-1 with a = 8.028(11) angstrom, b = 12.316(17) angstrom, c = 18.14(3) angstrom, alpha = 97.191(10)degrees, beta = 94.657(10)degrees and gamma = 108.039(10)degrees. It is single helical with the metal having a distorted trigonal bipyramidal N(4)O coordination sphere. The acid dissociation constant of the Cu(I) complex in CH(3)CN is 3.34 +/- 0.19. The X band EPR spectrum of the compound is rhombic with g(1) = 2.43, g(2) = 2.10 g(3) = 2.02 and A(1) = 79.3 x 10(-4) cm(-1). The Cu(II/I) potential of the complex in CH(2)Cl(2) at a glassy carbon electrode is 0.43 V vs SCE. It is argued that the copper-water bond persists in the corresponding copper(I) species. Its implications on the single helix-double helix interconversion in copper helicates are discussed. DFT calculations at the B3LYP/6-311G** level shows that the binding energy of water in the single helicol live-coordinate copper(I) species [CuL(H(2)O)](+) is similar to 40 kJ mol(-1).

Lightly branched comb polyesters: application in fast drying solvent-borne coating formulations

Novel oxazoline-based comb-polymers possessing linoleyl or oleic side chains have been synthesized and used to produce low viscosity coatings. Inclusion of the polymers in model paint formulations results in coatings that exhibit faster drying times than commercially available alkyd resin formulations. The comb polymers were produced from diol substituted oxazoline monomers that were synthesized through a scalable, solvent free protocol and purified by simple recrystallisation. Co-polymerisation of the oxazolines with adipic acid at 160 °C in the bulk resulted in the targeted polyester comb type polymers. The polymers were soluble in a range of organic solvents and compatible with commercial alkyd resins. Model paint formulations containing up to 40 wt% of the linoleyl-based comb polymers exhibited a dramatic reduction in viscosity (from 35 to 13 Poise at 25 °C) with increasing quantities of polymer added. Dynamic mechanical analysis (DMA) studies revealed that the drying rate of the model paint formulations containing the comb polymers was enhanced when compared with that of commercial alkyd resins.