Electronic and bonding properties of mono-ruthenium-substituted Keggin-type polyoxometalates: A theoretical study of [PW ~(11)O ~(39)Ru~(II/III)(L)] ~(n -) (L = dimethyl sulfoxide (DMSO), water, pyridine, and ammonia) and [GeW ~(11)O ~(39)Ru~(II)(DMSO) ~3(H ~2O)]~(6-)

摘要

The electronic structure and bonding feature of a series of mono-ruthenium-substituted Keggin-type polyoxometalates (POMs) have been investigated by using density functional theory (DFT) calculation, natural bond orbital (NBO) analysis and energy-decomposition analysis (EDA). A comparison of the electronic properties of two known dimethyl sulfoxide (DMSO)-supported mono-ruthenium-substituted Keggin-type POMs shows that both complexes have the analogous frontier-molecular orbital feature. One of them possesses a relatively small HOMO-LUMO gap because of the high HOMO energy level. This difference comes from a high composition of POM ligand with antibonding feature in HOMO. In addition, three typical Keggin-type POM complexes [PW11~(O39)Ru ~(II/III)(L)]~(n-) (L = H~2O, C~5H ~5N, NH~3) have also been explored according to our computational studies. The NBO analysis shows that the Ru~(II/III)-L bond comes from donor-acceptor interactions between the end ligand and the ruthenium (II/III) centre. The EDA shows that the POM complex [PW ~(11)O~(39)Ru~(II)(C~5H~5N)] ~(5-) has much stronger Ru~(II)-L bond than ammonia-supported Keggin-type POM [PW11~(O39)Ru~(II)(NH~3)] ~(5-). And the enhancement of the Ru~(II)-L bonding interaction in [PW11~(O39)Ru~(II)(C~5H5~N)]~(5-) is mainly due to the large orbital interaction energy ΔEorb. The ammonia-supported Keggin-type POM [PW11~(O39)Ru~(II)(NH ~3)]~(5-) and the aqua-ruthenium derivative [PW ~(11)O~(39)Ru~(II)(H~2O)]~(5-) have an analogous magnitude of the total bond energy. This result supports a non-aqueous environment for synthesis of an ammonia-supported Keggin-type POM [PW11~(O39)Ru~(II)(NH~3)]~(5-).