Hydrogen-bonding-induced solvatochromism in the charge-transfer transitions of ruthenium(II) and ruthenium(III) ammine complexes

Abstract

the diketone groups and the chelating atom of the adduct. A postulated intramolecular exchange mechanism has the adduct rise above this plane and rotate about the uranyl axis to the other side.2b If this mechanism is correct, one would expect a greater activation energy for intramolecular exchange the greater the distance of the uranium above the plane of the ligands. These distances and the activation energies are listed in Table IV. There is not good agreement between the two sets of parameters.Another possible intramolecular exchange mechanism is the rotation of the /3-diketone ring about an axis perpendicular to that of the uranyl group. This would have the effect of changing the positions of two, rather than all four, of the trifluoromethyl groups. It is reasonable to suppose that the more nearly planar the /3-diketone ring the more easily it might rotate. In Table IV are listed the maximum deviations from planarity for a carbon in each of the /3-diketone rings of the adduct. There is a good correlation between these deformations and the activation energy for trifluoromethyl exchange, except for the azide adduct. In this case it is not possible to determine which of the two isomers observed in solution is isolated in the solid. If it is the more rapidly averaging isomer, which would have a lower activation energy than that reported, then the correlation is good for all the compounds. It is therefore suggested that in these adducts the exchange occurs by rotation of the 3-diketone ring. ConclusionsTwo different structural forms of the azide and fluoborate adducts coexist in sulfur dioxide solution. The higher energy form has a faster averaging for the trifluoromethyl groups in both adducts. There are two concurrent exchange mechanisms for the tetrahydrofuran and chloride adducts. The lower energy pathway is by an intermolecular displacement mechanism, and the higher energy one by an intramolecular exchange. In all the adducts the intramolecular exchange probably occurs by rotation of the 3-diketone ring.

Efficient, Reversible Redox-Switching of Molecular First Hyperpolarizabilities in Ruthenium(II) Complexes Possessing Large Quadratic Optical Nonlinearities

“…[16] Their absolute magnitudes are hence of questionable accuracy and should not be compared with the data obtained in nonaqueous solvents (Table 1) 3 moiety is a powerful electron-withdrawing group which can engage in visible ligand-to-metal charge-transfer (LMCT) excitations when coordinated to donor-substituted ligands. [18] Indeed, other workers have previously demonstrated the use of this acceptor function in mixed-valence complexes possessing relatively large b values.…”

Miniaturized Reference Electrodes. II. Use in Corrosive, Biological, and Organic Media

“…The distance between WE and RE was set to 1 cm for all determinations. Over the past two decades the influence of the solvent on both the spectroscopic properties [27] and electrochemical potentials [26,28,29] of various metallic complexes has been studied. The formal potentials obtained by us for Fc-CH 2 OH in different organic media are in agreement with the values reported by Lay and co-workers [26] for various Fc þ/ 8 couples.…”

Substituent and Solvent Effects on the Electrochemical Properties and Intervalence Transfer in Asymmetric Mixed‐Valent Complexes Consisting of Cyclometalated Ruthenium and Ferrocene

“…The complexes studied all contained a {MA C H T U N G T R E N N U N G (NH 3 ) n } moiety, in which specific NH 3 -solvent hydrogen-bonding interactions were thought to play a decisive role. [31] However, solvent-solute interactions in complexes 6 ) in a solvent with higher donicity, for example, acetone, may be attributed to increasingly stronger solvation of the analyte by the stronger donor solvent. A similar trend was previously found by Geiger and Barrire in an electrochemical study on a bis-(fulvalene)dinickel complex in different solvents.…”