1410055-33-2Relevant articles and documents
Design, synthesis, magnetic properties of a π-radical ligand with photo-excited high-spin state and its Fe(ii) complex. the first stage of a new strategy for LIESST materials
Katayama, Koichi,Hirotsu, Masakazu,Kinoshita, Isamu,Teki, Yoshio
, p. 13465 - 13473 (2012)
A π-radical ligand (9-[4-(6-oxo-1,5-dimethylverdazyl)phenyl]-10-[5-(2, 2′-bipyridyl)ethynyl]anthracene, L1) with a photo-excited high-spin quartet state (S = 3/2) and its iron(ii) complex [Fe(L 1){H2B(Pz)2}2] (1) {H 2B(Pz)2- = dihydrobis(1-pyrazolyl)borate} were synthesized as a candidate for a new strategy for spin-crossover compounds exhibiting light-induced excited spin state trapping (LIESST), which is via the photo-excited high-spin state of the π-conjugated aromatic system. Control compounds, ligand L2 and [Fe(L2){H2B(Pz) 2}2] (2), in which the verdazyl radical moiety in L 1 was removed, were also synthesized. The photo-excited quartet state of the π-radical ligand L1 was confirmed by the time-resolved ESR technique. Temperature dependence of the magnetic behaviors of 1 and 2 were investigated from 5 K to 350 K, showing spin-crossover transition at T c = 222 K and at Tc = 162 K for complexes 1 and 2, respectively. The transition enthalpies and entropies were determined to be ΔH = 8.09 kJ mol-1 and ΔS = 36.4 J K-1 mol-1 for 1 and to be ΔH = 22.39 kJ mol-1 and ΔS = 138 J K-1 mol-1 for 2. LIESST phenomena were also observed below ca. 50 K for both complexes. The effects of the attachment of radical moiety are discussed based on the results.
