Spin Crossover in cis Manganese(III) Quinolylsalicylaldiminates. Issue 15 (27th April 2015)

• Record Type: Journal Article
• Authors: Sirirak, Jitnapa; Harding, David J.; Harding, Phimphaka; Murray, Keith S.; Moubaraki, Boujemaa; Liu, Lujia; Telfer, Shane G.
• Is Part Of: European journal of inorganic chemistry. Issue 15(2015)
• Page Start: 2534
• Page End: 2542
• Publication Date: 2015-04-27
• Subjects: Spin crossover -- Manganese -- Schiff base ligands -- Redox activity -- DFT calculations; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201500196
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: Two new Mn II/III redox pairs, [Mn(qsal‐Cl)2 ] 0/+ 1 0/+ and [Mn(qsal‐Br)2 ] 0/+ 2 0/+ have been synthesized employing the tridentate Schiff base ligands, 5‐X– N ‐(8‐quinolyl)salicylaldimine (Hqsal‐X, X = Cl and Br). The neutral Mn II complexes1 and2 were prepared from MnCl2 and Hqsal‐Cl and Hqsal‐Br while oxidation of1 or2 with AgOTf yields the cationic Mn III complexes, [Mn(qsal‐Cl)2 ]OTf, 1 +, and [Mn(qsal‐Br)2 ]OTf, 2 + .1 and2 have been characterized by single‐crystal X‐ray diffraction as CH2 Cl2 solvates. The Mn centres adopt a strongly distorted octahedral geometry with cis O donors due to the pair of meridionally bound qsal‐X ligands. Electrochemical studies indicate two reversible one‐electron redox processes, Mn 2+/3+ and Mn 3+/4+ . Spectroscopic studies show the LMCT bands move to lower wavelengths by ca. 30 nm while the νC=N stretches are little changed in the cationic complexes. Variable temperature magnetic susceptibility measurements indicate that1 + and2 + undergo gradual half spin crossover, despite having cis O donors. DFT calculations reveal a small HS–LS gap in the Mn III systems consistent with spin crossover and provide insight into the ligand design necessary for spin crossover in cis ‐N4 O2 Mn III compounds. Abstract : We report the redox pairs [Mn(qsal‐X)2 ] 0/+ in which the Mn III cations exhibit spin crossover despite the cis O donors.