Spin Relaxation in Ru‐Chromophore‐Linked Azine/Diquat Radical Pairs

Photoinduced Intercomponent Processes in Selectively Addressable Bichromophoric Dyads Made of Linearly Arranged Ru(II) Terpyridine and Expanded Pyridinium Components

“…Beyond any consideration on their relative energies ( 3 CS should be slightly lower in energy than 1 CS), charge recombination, leading to a singlet ground state, would be a spin-forbidden process for 3 CS and a spin-allowed one for 1 CS. In other covalently linked systems a similar situation was considered and changes in rate constants for charge recombination involving singlet and triplet charge-separated states have been calculated and/or measured. , In such cases, it appeared that the differences between spin-allowed and spin-forbidden CR processes are not obvious, and energetic factors connected with Marcus theory should also be considered and can play a major role with respect to spin rules . In some cases, large rate constant differences have been reported in favor of spin-allowed CR, but the spin-allowed route was there activated by an incoherent mechanism, which is excluded in our case.…”

Complete Monitoring of Coherent and Incoherent Spin Flip Domains in the Recombination of Charge-Separated States of Donor-Iridium Complex-Acceptor Triads

“…The dominating hyperfine interaction is due to the 14 N nucleus of the triarylamine radical moiety. For negligible g-tensor anisotropy the transversal relaxation time is given by 44 Directly applicable literature data on the anisotropy of hyperfine coupling ΔA of the N atom in the present triarylamine radical moieties are not available, but quantum chemical calculations for phenoxazine radicals 45 and for its sulfur and selenium heteroanalogues have shown that the anisotropy ΔA of hyperfine coupling of the 14 N atom is about 2.7 times its isotropic value, which indicates that it results mainly from the dipolar interaction between the nuclear spin and the electron spin in the 2p orbital and only a small part of the isotropic hyperfine interaction is due to spin polarization of the 2s orbital. About the same ratio is obtained for the inorganic radicals N(SO 3 ) 2 2− and NH(SO 3 ) − .…”

“…Relating the parameters in equation (13) Directly applicable literature data on the anisotropy of hyperfine coupling A ∆ of the N atom in the present triarylamine radical moieties are not available, but quantum chemical calculations for phenoxazine radicals 45 and for its sulfur and selenium heteroanalogues have shown that the anisotropy A ∆ of hyperfine coupling of the 14 N atom is about 2.7 times its isotropic value, which indicates that it results mainly from the dipolar interaction between the nuclear spin and the electron spin in the 2p orbital and only a small part of the isotropic hyperfine interaction is due to spin polarization of the 2s orbital. About the same ratio is obtained for the inorganic radicals The regime of incoherent spin flip at B > 1 T. The magnetic field independent contributions rel,∞ k to the rate constants k ± were found to be 3.1•10 5 s -1 for triad 1 and 1.64•10 5 s -1 for triad 3.…”

Spin-chemical effects on intramolecular photoinduced charge transfer reactions in bisphenanthroline copper(i)-viologen dyad assemblies

“…† Although the nature of the relaxation process dominating at high field which formally corresponds to an internal modulation of g -tensor anisotropy is not yet clear, we note that similar observations have been made for [RuL 3 ] 2+ -based D–C–A triads with a phenoselenazine donor and a diquaternary amine acceptor. 34 , 35 In that case, a correlation time of 2 ps and a modulation by the full g -tensor anisotropy have been found.…”

“…The greater physical separation between radical species and different spin-chemical interactions in the [RuL 3 ] 2+ -based D–C–A species enables much longer lifetimes to be achieved. 34 , 39 – 42 However, as mentioned above, copper C–A dyads can already exhibit longer lifetimes of the C + –A – , CT state. Yet, the question of their spin chemistry is interesting and has not been explored.…”