Behind the scenes of spin-forbidden decay pathways in transition metal complexes

Abstract

The interpretation of the ultrafast photophysics of transition metal complexes following photoabsorption is quite involved as the heavy metal center leads to a complicated and entangled singlet-triplet manifold. This opens...

On the intersystem crossing rate in a Platinum(ii) donor–bridge–acceptor triad

“…Together, FLUP and FSR allows one to resolve the dynamics of multiple states which evolve simultaneously on a sub-ps time-scale. Comparing FLUP and FSR results for [1]- [3], alongside with transient absorption and transient infrared data, we show that the strength of radiative coupling to the electronic ground state remains constant during the decay process, at a value similar to that of (strong) absorption. It follows that the emissive manifold is of primarily singlet spin-orbit character.…”

“…Transient absorption spectra of NAP-Pt-Cl [3] and NAP-Pt-PTZ [1] recorded here are shown in Fig. 1a and Fig.…”

“…Multi-exponential global fits were carried out for the time range from -1 ps to 4 ns. To achieve a satisfactory fit to the spectral changes, three exponential components and one long-lived component were required for [3] (best fit:  a = 0.97 ps,  b = 59 ps,  c = 193 ps). Four exponential components and one long-lived component were required for [1] (best fit:  a = 0.50 ps,  b = 2.46 ps,  c = 10.57 ps, and  d = 742 ps; see Table 1 and the SI).…”

“…[2][3][4][5][6][7][8] Numerous observations of ISC in metal complexes have been reported in the past two decades, containing, for example Cr, 9,10 Fe, [11][12][13][14][15][16][17] Cu, 18 Zn, 19 Ni, 20 Ru, [21][22][23][24][25][26] Re, 27 Os, 28 Pt, 20,[29][30][31][32][33][34][35][36] or Pd 20 , or Mo 37 . ISC has been reported to occur in metal complexes over a large range of timescales, from < 30 fs 11,38 to hundreds of picoseconds, but it is not clear yet what mechanisms govern the rates of ISC, 3 which can be vastly different even in compounds of similar structure. 29 There may be dependence of ISC rates upon metal-ligand bond stretch frequency, 27 ligand size, 29 and in some cases solvent.…”

The Quest to Simulate Excited-State Dynamics of Transition Metal Complexes

“…eq 6 ). However, when intersystem crossing is too slow, time scales can be obtained indirectly from static calculation of intersystem crossing rates, 12 , 26 , 265 e.g., based on Fermi’s golden rule The molecular wave functions Ψ mol are thereby taken as a product of an electronic and a nuclear part, the latter typically approximated by harmonic oscillators, and all coupling elements are calculated at a reference geometry for which usually the equilibrium geometry of the initial state is selected. This approach has been used to calculate intersystem crossing rates for a number of transition metal complexes.…”