Synthesis and vibrational spectra of metal halide complexes of 8-hydroxyquinoline in relation to their structures

Complexes of the type M(8-HOQ)2X2 (where M ¼ Zn, Co; X ¼ Cl, Br, I and M ¼ Fe, X ¼ Cl; 8-HOQ ¼ (C9H7NO), 8-hydroxyquinoline) have been studied in the 4000–200 cm21 region, and assignment of all the observed bands were made. The analysis of the vibrational spectra indicates that there are some structure-spectra correlations. For a given series of isomorphous complexes the sum of the difference between the values of the vibrational modes of uncoordinated 8-hydroxyquinoline and coordinated to metal ion 8-hydroxyquinoline was found to increase in the order of the second ionization potentials of metals. The frequency shifts were also found to depend on the halogen. Certain chemical formulas were determined using elemental analysis results. q 2003 Elsevier B.V. All rights reserved.