Control Of Exchange Interaction Research Articles

Control of Exchange Interactions in π Dimers of 6‐Oxophenalenoxyl Neutral π Radicals: Spin‐Density Distributions and Multicentered–Two‐Electron Bonding Governed by Topological Symmetry and Substitution at the 8‐Position

The tri-tert-butylphenalenyl (TBPLY) radical exists as a π dimer in the crystal form with perfect overlapping of the singly occupied molecular orbitals (SOMOs) causing strong antiferromagnetic exchange interactions. 2,5-Di-tert-butyl-6-oxophenalenoxyl (6OPO) is a phenalenyl-based air-stable neutral π radical with extensive spin delocalization and is a counter analogue of phenalenyl in terms of the topological symmetry of the spin density distribution. X-ray crystal structure analyses showed that 8-tert-butyl- and 8-(p-XC6H4)-6OPOs (X=I, Br) also form π dimers in the crystalline state. The π-dimeric structure of 8-tert-butyl-6OPO is seemingly similar to that of TBPLY even though its SOMO-SOMO overlap is small compared with that of TBPLY. The 8-(p-XC6H4) derivatives form slipped stacking π dimers in which the SOMO-SOMO overlaps are greater than in 8-tert-butyl-6OPO, but still smaller than in TBPLY. The solid-state electronic spectra of the 6OPO derivatives show much weaker intradimer charge-transfer bands, and SQUID measurements for 8-(p-BrC6H4)-6OPO show a weak antiferromagnetic exchange interaction in the π dimer. These results demonstrate that the control of the spin distribution patterns of the phenalenyl skeleton switches the mode of exchange interaction within the phenalenyl-based π dimer. The formation of the relevant multicenter-two-electron bonds is discussed.

Control of Exchange Interactions in Trinuclear Complexes Based on Orthogonal Magnetic Orbitals

AbstractThe reaction of copper(II) acetate with the tetradentate Schiff base like ligand H4L {(E,E)‐[{diethyl 2,2′‐[4,5‐dihydroxy‐1,2‐phenylenebis(iminomethylidyne)]bis(3‐oxobutanoate)}] leads to the formation of the square planar N2O2 coordinated complex [H2CuL]. Reaction of two equivalents of this complex with copper(II) acetylacetonato or vanadyl(IV) acetylacetonato yields the trinuclear complexes [V(O)Cu2L2][N(nBu)4]2·2MeOH (1) and [Cu3L2][N(nBu)4]2·2DMF (2). Both complexes were characterised by using magnetic measurements and X‐ray crystallography. Special attention was given to the spin‐exchange coupling through the bridging phenylene ring. The principle of strict orthogonality of the magnetic orbitals can be applied to explain the results of the susceptibility measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

分子スピン量子コンピュータのモデル系・新規ビラジカルの設計と合成: ビスデュレン架橋による交換相互作用の制御とg-engineeringの検討

分子スピン量子コンピュータのモデル系・新規ビラジカルの設計と合成: ビスデュレン架橋による交換相互作用の制御とg-engineeringの検討