S.I Gorelsky

ELECTRONIC STRUCTURE AND SPECTRA OF RUTHENIUM DIIMINE COMPLEXES BY DENSITY FUNCTIONAL THEORY AND INDO/S. COMPARISON OF THE TWO METHODS

Density functional theory calculations have been carried out on the series [Ru(bqdi)n(bpy)3−n]2+ (bpy=2,2′-bipyridine, bqdi=o-benzoquinonediimine) to explore the extent of coupling between metal 4d and ligand π and π* orbitals. Time-dependent density-functional response theory (TD-DFRT) has been used to predict the complex electronic spectra which are compared with their experimental data. The main thrust of the paper is a comparison of these calculations with those carried out using Zerners frequently used INDO/S method. Different procedures for the electron population analysis of molecular orbitals are described and discussed. The agreement in terms of orbital energies, orbital mixing and electronic spectra is remarkably good. This confirms that for these species, and probably for all non-solvatochromic species in general, INDO/S is a good model reproducing very well the results of the computationally much more demanding, but also more reliable TD-DFRT calculations.

Trends in metal–ligand orbital mixing in generic series of ruthenium N-donor ligand complexes—effect on electronic spectra and redox properties

Abstract Generic series of complexes [Ru(bpy) 3− n (LL) n ] 2+ (bpy=2,2′-bipyridine), where LL is a diimine ligand including specifically 2,2′-bipyrazine (bpz), 2,2′-azobipyridine (abpy), and o -benzoquinonediimine (bqdi), are studied with respect to their electrochemistry, optical spectroscopy and electronic structure as elucidated using Zerners INDO/S method. Characteristics of their electrochemistry and optical spectroscopy are explained in terms of mixing between ruthenium d orbitals and diimine ligand π and π* orbitals, increasing in importance from bpy to bpz to abpy to bqdi. In this last case, these species have characteristics not unlike fully delocalized organic molecules.

Synthesis, spectroscopic and a ZINDO study of cis- and trans-(X2)bis(4,4'-dicarboxylic acid-2,2'-bipyridine)ruthenium(II) complexes (X = Cl-, H2O, NCS-)

Reference LPI-ARTICLE-2000-005doi:10.1016/S0010-8545(00)00338-6View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Ruthenium d-orbital delocalization in bis(bipyridine)ruthenium derivatives of redox active quinonoid ligands

Abstract Density Functional Theory (DFT) and INDO in the version developed by Zerner (ZINDO) are used to describe how the electronic coupling (π-back-donation etc.) in the series [Ru(bpy)2(LL)]2+ vary as a function of the coordinating atoms of LL. The bidentate ligand LL is o-benzoquinonediimine (NH·NH), and derivatives where one imino group is replaced by oxygen (NH·O) and by sulfur (NH·S). The electronic spectra of these species are calculated using both the INDO/S and time dependent DFRT models and compared with the experimental data. The agreement is excellent. The extent of interaction between the ruthenium dπ orbitals and LL increases in the sequence (NH·NH)

Electronic spectra of trans-[Ru(NH3)4(L)NO]3+/2+ complexes

Density functional theory (DFT) with local, non-local and hybrid functionals has been used to obtain the geometry of a series of nitrosyl–metal complexes [Ru(NH3)4(L)NO]n+, where L=NH3, H2O, pyrazine and pyridine (n=3), Cl− and OH− (n=2). Based on the molecular orbital analysis and the time dependent DFT (TD-DFT) calculations, we discuss the electronic structure and the assignment of the bands in the electronic spectra of these complexes.

Metastable states of ruthenium (II) nitrosyl complexes and comparison with [Fe(CN)5NO]2−

The properties of the [Ru(NH3)5NO]3+ and [Ru(CN)5NO]2− ions are investigated by density functional theory and compared with those of [Fe(CN)5NO]2−. DFT calculations show that the electronic ground-state potential surface of these nitrosyl complexes has local minima (metastable states) with oxygen-bonded NO (MS1), i.e., inverted from the usual N-bonded species (GS), and with NO which is bound sideways (η2-MS2). In [Ru(CN)5NO]2− and [Fe(CN)5NO]2− ions, the MS2 state lies 1.1–1.4 eV above the GS state and 0.3–0.6 eV below the MS1 state, but in the [Ru(NH3)5NO]3+ ion, the MS2 state is slightly above the MS1. In the visible region, the electronic spectrum of ruthenium nitrosyl complexes contains metal-to-ligand charge transfer bands, 4dπ(Ru)e(π* NO). Using time-dependent density functional theory calculations it is possible to explain why the MS2 state of [Ru(NH3)5NO]3+ has not been observed experimentally.

Comparison of o-benzoquinonediimine with bipyridine and bipyrazine in electronic coupling to ruthenium(II), as a function of spectator ligand

Abstract When comparing [Ru(LL) 3 ] 2+ with [Ru(NH 3 ) 4 (LL)] 2+ , the question is raised whether the replacement of the relatively poor LL (LL=2,2′-bipyridine, 2,2′-bipyrazine or o -benzoquinonediimine) π-acceptor and σ-electron ligands by the σ-electron rich ammonia ligands permits a significant improvement in coupling/π-back donation to the remaining LL. Using a zindo analysis of the electronic structures of these species, it is shown that 2,2′-bipyridine is unable to accept the extra electron density from the ruthenium center, while o -benzoquinonediimine can readily do so. The ligand 2,2′-bipyrazine is slightly more able to accept the electron density than 2,2′-bipyridine.

When does the Hard and Soft Acid Base principle apply in the gas phase

Abstract We have studied the silver ion affinities of several RCN ligands using density functional theory. It was found that they correlate linearly with experimental proton affinities, a contradiction to the HSAB principle as H + is a ‘hard’ acid, and Ag + is a ‘soft’ acid. This linear correlation between the Ag + and proton affinities diminishes as the number of RCN ligands attached to the Ag + ion increases from one to three. In the third addition step, the silver ion affinities nearly level off in agreement with the expectation that the electron donating or withdrawing properties of the R group become much less important than in the previous two steps, where the positive charge on the metal ion is not well delocalized. Delocalization of the charge of a metal ion occurs only when a sufficiently large number of ligands are attached to the metal ion. When this condition is satisfied, our data suggests that the HSAB principle may be applicable.