Thermal studies of copper(II) squarate complexes of diamines in the solid state

CuL2C4O4 [L=ethane-1,2-diamine (en)], CuL2C4O4.2H(2)O [L=N-methylethane-1,2-diamine (meen), N-ethylethane-1,2-diamine (eten), N-propylethane-1,2-diamine (pren), N-methyl-N'-ethylethane-1,2-diamine (meeten) and propane-1,2-diamine (pn)], CuL2C4O4.0.5H(2)O [L=N,N'-dimethylethane-1,2-diamine (dmeen)], CuL2C4O4.4H(2)O [L=propane-1,2-diamine (pn)] and CuL2C4O4-.H2O [L=2-methylpropane-1,2-diamine (ibn)] have been synthesized by the addition of respective diamine to finely powdered CuC4O4.2H(2)O and their thermal studies have been carried out in the solid state. Cu(en)(2)C4O4 upon heating loses one molecule of diamine with sharp colour change yielding Cu(en)C4O4 which upon further heating transforms to unidentified products. All aquated-bis-diamine species [CuL2C4O4.2H(2)O, CuL2C4O4.0.5H(2)O and CuL2C4O4.H2O] upon heating undergo deaquation-anation reaction in the solid state showing thermochromism and transform to CuL2C4O4, which revert on exposure to humid atmosphere (RH similar to90%), All the squarato bis-diamine species, CuL2C4O4, on further heating transform to unidentified products through the formation of CuLC4O4 as intermediates. The mono diamine species, have been isolated pyrolytically in the solid state and can be stored in a desiccator as well as in open atmosphere. They are proposed to be polymeric.