Ultrafast reversible ligand isomerisation in Na2[Fe(CN)5NO]·2H2O single crystals

Abstract

We present a time-resolved absorption study on the light-induced generation of reversible linkage NO isomers in single crystals of Na₂[Fe(CN)₅NO]·2H₂O using laser pulses of 160 fs width. Using the pump wavelength λ = 500 nm the singlet–singlet ¹A₁ → ¹E excitation induces the NO rotation by about 90° from the linear Fe–N–O configuration to a side-on configuration Fe<^N_O. The formation of the isomer is monoexponential with a characteristic time of τ = 300(20) fs and proceeds along a diabatic potential surface without occupation of further intermediate states. The side-on structure has a lifetime of 270(30) ns at T = 23 °C.