Light-Induced Excited Spin-State Properties in 1D Iron(II) Chain Compounds

With the ultimate goal of rationally studying the factor able to affect the stability of the photoinduced high-spin state, we selected three iron(II) 1D coordination polymers with the general formula [FeLeq(Lax)]·solvent with Leq = {3,3′-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentanedionato)(2-)-N,N′,O2,O2′}; Lax = 4,4′-bipyridine (bipy, 1), 1,2-bis(4-pyridyl)ethane (bpea, 2), and 1,3-bis(4-pyridyl)propane (bppa, 3); and solvent MeOH. This series of complexes comprises 1D chains with structures varying from linear (for bipy) over step-like (for bpea) to zigzag (for bppa). For all the materials, the thermal spin-crossover properties were measured and the stabilities of the photoinduced high-spin states were probed through determination of the T(LIESST) values associated with the light-induced excited spin-state trapping (LIESST) effect. For some of the investigated samples, the existence of steps in the relaxation of the photoinduced high-spin state was discussed.