Abstract
The new ligands L = 1,4-bis(2-methylchalcogenophenyl)-2,3-dimethyl-1,4-diaza-1,3-diene [chalcogen = O (1), S (2) or Se (3)] have been studied in their coordination behavior towards CuI and CuII. Whereas the O-ether contg. ligand forms complex ions [Cu(L)2]n+ = 4n+, with exclusive N-coordination (n = 1) or N and weaker O coordination (n = 2), the species with E = S or Se contain tetradentate ligands in [Cu(L)]+ (5+, 6+) and [Cu(L)L']n+ [n = 1, L' = TfO- (E = S) or n = 2 and L' = H2O (E = Se)]. Mol. structures in the crystals of 5+ and 6+ show distorted tetrahedral N coordination at the metal and innocently behaving a-diimine functions, in agreement with spectroscopic and computational data. The copper(II) ions [Cu(L)L']2+ with one tetradentate ligand L = 2 or 3 exhibit a square-pyramidal configuration at the metal. Two isolated cryst. forms of 42+ show weak coordination (2.636-2.96 \AA) of three or four ether oxygen atoms, resulting in 4+3 or 4+4 coordination arrangements for N and O donors, resp. In agreement with the rather different CuI and CuII structures the electrochem. oxidn. of the copper(I) complexes and the redn. of the corresponding CuII species reveal an ECEC behavior within a square scheme, whereas the redn. of the CuI compds., most likely at the diimine site, proceeds irreversibly. UV/Vis spectroelectrochem. results showing intense MLCT and IL absorptions were analyzed with the help of TD-DFT calcns. [on SciFinder(R)]
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