Spin–orbit induced radiationless transitions in organometallics: Quantum simulation of the 1E→3A1 intersystem crossing process in HCo(CO)4

Abstract

Spin-orbit coupled excited states in transition metal complexes: A configuration interaction treatment of HCo(CO)4A theoretical description of the ''fast'' ͑Ͻ50 ps͒ intersystem crossing processes occurring at critical geometries during the photodissociation of HCo͑CO͒ 4 is presented. The radiationless transitions are simulated by wave packet propagations along one-dimensional reaction coordinate on the spin-orbit coupled potential energy surfaces. The propagation are performed separately, either along the Co-H bond or along the Co-CO ax bond. This original approach has enabled us to understand the mechanism of desactivation of the initially populated singlet excited state in this molecule which should be considered as a model for other organometallics. We propose the following mechanism: ͑i͒ in a very short time scale ͑Ͻ20 fs͒ 40% of the system dissociates towards the primary products HϩCo͑CO͒ 4 ( 1 E), whereas the 1 E→ 3 A 1 intersystem crossing along the Co-H bond elongation occurs within 50 ps; ͑ii͒ the dissociation of an axial carbonyl ligand occurs in a larger time scale ͑200 fs͒ and only 2% of the system dissociates along the Co-CO ax elongation. The dominant process is the 1 E→ 3 A 1 intersystem crossing leading to HCo͑CO͒ 4 ͑ 3 A 1 ͒; ͑iii͒ as soon as the lowest triplet state is populated, the system dissociates either to HϩCo͑CO͒ 4 or to HCo͑CO͒ 3 ϩCO ax on the 3 A 1 potential energy surface; ͑iv͒ the intersystem crossing process may be described as a succession of elementary transitions occurring at critical geometries or crossing points between the singlet and the triplet potential energy surfaces; ͑v͒ the efficiency of the radiationless transition is governed by the overlap of the propagated wave packet with the critical region of the coupled potential energy surfaces.

Relativistic effects in spectroscopy and photophysics of heavy-metal complexes illustrated by spin–orbit calculations of [Re(imidazole)(CO)3(phen)]+

“…For example, the spin-free a 3 B 2 state is split by ∼3000 cm −1 , contributing 40-50% to several SO states. Interesting are CASSCF-type calculations of SOC effects on nonradiative photophysical and photochemical behavior, for example, intersystem crossing in HCo(CO) 4 [108], M-H bond photodissociation in [M(H)(CO) 3 (1,4-diazabutadiene)] [109], and intraligand trans-cis isomerization in [Re(styrylpyridine)(CO) 3 (bpy)] + [19,110]. Emission from SO states has been investigated for OLED-relevant Pd(thpy) 2 and Pt(thpy) 2 cyclometallated complexes by relativistic multiconfiguration SCF [111].…”

A general method to describe intersystem crossing dynamics in trajectory surface hopping

“…A number of studies have used quantum wavepacket dynamics, where inclusion of SOC is straightforward; however, these studies are usually restricted to few degrees of freedom. Examples include dihalogens in argon matrices, [80][81][82] transition-metal complexes, [83][84][85][86][87][88][89][90][91][92][93][94][95] and collision reactions. [96] Further, quantum dynamical studies investigated ISC in benzene, [97] hydrogen fluoride, [98] and sulphur dioxide.…”

Nonadiabatic Effects in the Photodissociation and Electronic Spectroscopy of HMn(CO)3(dab): Quantum Wave Packet Dynamics Based onab InitioPotentials

“…Work along these lines is in progress and has in fact also been done for other transition metal compounds. 21 Further, excited states of A′′ symmetry should be included. Finally, in view of possible applications offered by the concept of the "bond selective chemistry", the inclusion of two competing reaction channels, namely, the homolytic breaking of the Mn-H bond and the heterolytic loss of CO, will be an interesting line of future research.…”

“…[15][16][17][18] In a second step, time-dependent quantum wave packet propagation methods can be used to characterize the photodissociation dynamics. [19][20][21][22] Additionally, the time-dependent wave packet approach may also be employed to calculate electronic emission or absorption spectra. 23,24 For the model diimine complex HMn(CO) 3 (dab) (dab ) 1,4-diaza-1,3-butadiene), we have speculated in a recent work 25 on the basis of the potential energy curves (PECs) computed for the metal-hydrogen bond cleavage reaction that an unbound 3 LLCT (ligand-to-ligand charge transfer) (σ f π*) excited state might be responsible for the metal-hydrogen bond homolysis.…”