Abstract
A b s t r a c t: In order to get a more exact basis for the band assignments in the case of dichlorodioxochromium(VI) complex with 1,10-phenanthroline (especially regarding the order of appearance of the antisymmetric and symmetric CrO2 stretching bands) a quantum chemical study of this system was carried out. Two levels of theory were employed – the HF/6-31++G(d,p) and the density-functional-theory-based (DFT) method B3–LYP/6- 31++G(d,p). Full geometry optimizations of the title complex were carried out, employing Schlegel's gradient optimization algorithm. Harmonic vibrational analyses of the stationary points located on both potential energy hypersurfaces were subsequently carried out in order to test their character and to compute the harmonic vibrational frequencies of the complex. Predictions of the ab initio and DFT quantum chemical approaches regarding the order of appearance of the antisymmetric and symmetric CrO2 stretching bands in the case of the studied complex were compared to the cases of analogous 2,2'-bipyridine and 2,2'-biquinoline complexes containing the CrO2 group, which were previously studied by us [1–6].
Highlights
Some time ago, while spectroscopically studying the MO2Cl2 (M ∈ {Cr, Mo, W}) complexes with 2,2'-bipyridine [1], a clear trend was observed concerning the separation between the bands originating from the essentially pure O=M=O stretching modes
The preliminary ab initio calculations showed that the symmetric stretching frequency in the case of the tungsten compound is higher than the antisymmetric one and an analogous situation was encountered in WO2(H2N–CH2–NH2)Cl2 and WO2(NH3)2Cl2 – two hypothetical compounds modelling the experimentally studied WO2(bpy)Cl2
It appeared to be advantageous to check whether the situation would be analogous in the case of the CrO2Cl2 complex with 1,10-phenanthroline – a ligand similar to 2,2'-bipyridine but larger than it
Summary
While spectroscopically studying the MO2Cl2 (M ∈ {Cr, Mo, W}) complexes with 2,2'-bipyridine [1], a clear trend was observed concerning the separation between the bands originating from the essentially pure O=M=O stretching modes (groups of bands rather than single ones were observed). The preliminary ab initio calculations (performed at the HF SCF level of theory) showed that the symmetric stretching frequency in the case of the tungsten compound is higher than the antisymmetric one and an analogous situation was encountered in WO2(H2N–CH2–NH2)Cl2 and WO2(NH3)2Cl2 – two hypothetical compounds modelling the experimentally studied WO2(bpy)Cl2.
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