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. Issue 36 (6th August 2013)

• Record Type: Journal Article
• Authors: Nishida, Shinsuke; Kawai, Junya; Moriguchi, Miki; Ohba, Tomohiro; Haneda, Naoki; Fukui, Kozo; Fuyuhiro, Akira; Shiomi, Daisuke; Sato, Kazunobu; Takui, Takeji; Nakasuji, Kazuhiro; Morita, Yasushi
• Is Part Of: Chemistry. Volume 19:Issue 36(2013)
• Page Start: 11904
• Page End: 11915
• Publication Date: 2013-08-06
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201301783
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The tri‐<italic>tert</italic>‐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‐<italic>tert</italic>‐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‐<italic>tert</italic>‐butyl‐ and 8‐(<italic>p</italic>‐XC<sub>6</sub>H<sub>4</sub>)‐6OPOs (X=I, Br) also form π dimers in the crystalline state. The π‐dimeric structure of 8‐<italic>tert</italic>‐butyl‐6OPO is seemingly similar to that of TBPLY even though its SOMO–SOMO overlap is small compared with that of TBPLY. The 8‐(<italic>p</italic>‐XC<sub>6</sub>H<sub>4</sub>) derivatives form slipped stacking π dimers in which the SOMO–SOMO overlaps are greater than in 8‐<italic>tert</italic>‐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‐(<italic>p</italic>‐BrC<sub>6</sub>H<sub>4</sub>)‐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.</p> </abstract>