The light-induced high-spin -> low-spin relaxation for the Fe(II) spin-crossover compounds [Fe(btpa)](PF6)(2) and [Fe(b(bdpa))](PF6)(2) in solution, where btpa is the potentially octadentate ligand N,N,N',N'-tetrakis(2-pyridylmethyl)6,6'-bis(aminomethyl)-2,2'-bipyridine and b(bdpa) is the analogous hexadentate ligand N,N'-bis(benzyl)-N,N'(2-pyridylmethyl)-6,6'-bis(aminomethyl respectively, has been studied by temperature-dependent laser flash photolysis. [Fe(b(bdpa))](PF6)(2) shows single-exponential T-5(2) -> (1)A(1) relaxation kinetics, whereas [Fe(btpa)](PS)(2) exhibits solvent-independent biphasic relaxation kinetics. The fast process of [Fe(btpa)](PF6)(2) with a rate constant, k(HL), Of 2.5 x 10(7) s(-1) at 295 K and an activation energy, E-a of 1294(26) cm(-1) in methanol can be assigned to the T-5(2) -> (1)A(1) relaxation as well. The slow process with a kHL(295 K) of 3.7 x 10(5) s(-1) and a E-a, of 2297(32) cm(-1) in methanol-which is the slowest light-induced relaxation process observed so far for an Fe(II) spin-crossover complex in solution-is assigned to a coupling of the T-5(2) -> (1)A(1) relaxation process to a geometrical rearrangement within the pendent pyridyl arms.