Infrared study of νOD modes in isotopically dilute (HDO) isostructural compounds M(HCOO)2•2H2O (M = Mn,Fe,Co,Ni,Cu,Zn) with matrix-isolated guest ions (Cu2+ in M(HCOO)2•2H2O and M2+ in Cu(HCOO)2•2H2O)

The infrared spectra of isotopically dilute (matrix-isolated HDO molecules) isostructural compounds M(HCOO)(2). 2H(2)O (M = Mn,Fe,Co,Ni,Zn,Cu) are presented and discussed in the region of the OD stretching modes. According to the structural data the compounds under study are divided into two groups: in M(HCOO)(2). 2H(2)O (M = Mn,Ni,Zn) the H2O(1) molecules form stronger hydrogen bonds as compared to H2O(2); in M(HCOO)(2). 2H(2)O (M = Fe,Co,Cu) the H2O(2) molecules form stronger hydrogen bonds as compared to the H2O(1) molecules. The influence of the metal-water interactions (synergetic effect) and the unit-cell volumes (repulsion potential of the lattice) on the hydrogen bond strength within the isostructural series is discussed. The wavenumbers of the uncoupled OD stretching modes of the HDO molecules influenced by guest ions (Cu2+ ions matrix-isolated in M(HCOO)(2). 2H(2)O and M2+ ions matrix-isolated in Cu(HCOO)(2). 2H(2)O) are presented and commented. For example, the analysis of the spectra reveals that when Cu2+ ions are included in the structure of M(HCOO)(2). 2H(2)O the hydrogen bonds of the type M-OH2. . . OCHO-Cu are considerably weaker as compared to those of the same type formed when M2+ ions are included in the structure of Cu(HCOO)(2). 2H(2)O if the cations remain unchanged. (C) 2001 Elsevier Science B.V. All rights reserved.