Thermal spin crossover behaviour of two-dimensional Hofmann-type coordination polymers incorporating photoactive ligands

Florence Ragon (1) , Korcan Yaksi (1) , Natasha F. Sciortino (1) , Guillaume Chastanet (2) , Jean-Francois Létard (2) , Deanna M. D’alessandro (1) , Cameron J. Kepert (1) , Suzanne M. Neville (1)

1 School of Chemistry
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

Two spin crossover (SCO)-active 2D Hofmann-type framework materials, [Fe(3-PAP)2Pd(CN)4] (A) and [Fe(4-PAP)2Pd(CN)4] (B) containing the photoactive azo-benzene-type ligands 3-phenylazo-pyridine (3-PAP) and 4-phenylazo-pyridine (4-PAP) were prepared. These materials form non-porous Hofmann-type structures whereby 2D [FeIIPd(CN)4] grids are separated by 3- or 4-PAP ligands. The iron(ii) sites of both materials (A and B) undergo abrupt and hysteretic spin transitions with characteristic transition temperatures T1/2↓,↑: 178, 190 K (ΔT: 12 K) and T1/2↓,↑: 233, 250 K (ΔT: 17 K), respectively. Photo-magnetic characterisations reveal light-induced excited spin state trapping (LIESST) activity in both A and B with characteristic T(LIESST) values of 45 and 40 K. Although both free ligands show trans- to-cis isomerisation in solution under UV-irradiation, as evidenced via absorption spectroscopy, such photo-activity was not observed in the ligands or complexes A and B in the solid state. Structural analysis of a further non-SCO active isomer to B, [Fe(4-PAP)2Pd(CN)4]·1/2(4-PAP) (B·(4-PAP)), which contains free ligand in the pore space is reported.

Domaines: Chimie de coordination; Cristallographie; Polymères

Florence Ragon, Korcan Yaksi, Natasha F. Sciortino, Guillaume Chastanet, Jean-Francois Létard, et al.. Thermal spin crossover behaviour of two-dimensional Hofmann-type coordination polymers incorporating photoactive ligands. Australian Journal of Chemistry, 2014, 67 (11), pp.1563-1573. ⟨10.1071/CH14188⟩. ⟨hal-01086433⟩