Gillian Murphy, Pat Nagle, Brian Murphy and Brian Hathaway
The crystal structures of [Cu(phen)2Cl][BF4]·0.5H2O 1 (phen = 1,10-phenanthroline), [Cu(phen)2Cl][PF6] 2, [Cu(phen)2Cl][CF3SO3]·H2 O 3 and [Cu(phen)2Cl][BPh4] 4 have been determined by X-ray crystallography. Three of the complexes, 1–3, involve a CuN4Cl chromophore with a square based pyramidal distorted trigonal bipyramidal stereochemistry, while 4 involves a trigonal bipyramidal distorted square based pyramidal stereochemistry. The geometries of the CuN4Cl chromophores in 1–4 were compared by scatter-plot analysis with those of four other [Cu(phen)2Cl][Y] complexes of known structure. The scatter plots of the eight cation distortion isomers of the [Cu(phen)2Cl][Y] complex suggest that all the complexes involve a -A + B route distortion of the CuN4Cl chromophore, -A (ca. 60%) and +B (ca. 40%), The observation of linear and parallel correlations are alternatively interpreted as a direct observation of vibronic coupling of a mixture of the symmetric, νsym, C2 mode and the asymmetric, νasym, non-C2 mode of vibration of the CuN4Cl chromophore. This emphasises the need to determine the structure of more than one complex in a series of cation distortion isomers, in which the limits of the range of stereochemistries are indicated by the measurement of the electronic reflectance spectra.