title: Ionic pair complexes with well-separated columnar stack structure based on [Pt(mnt)2]- ions showing unusual magnetic transition: syntheses, crystal structures, and magnetic properties.
abstract: Three ion pair complexes, [4-R-benzylpyridinium][bis(maleodinitriledithiolato)platinum(III)] (abbreviated as [RBzPy][Pt(mnt)(2)]; R = Cl (1), Br (2), or NO(2) (3)), have been synthesized. The cations and anions stack into well-separated columns in the solid state, and the Pt(III) ions form a 1-D zigzag chain within a [Pt(mnt)(2)](-) column through Pt...S, S...S, and Pt...S...Pt interactions. The chain is uniform in 1 and 2, while it alternates in 3. Unusual magnetic phase transitions from paramagnetism to diamagnetism were observed in these three complexes at approximately 275 K for 1, approximately 269 K for 2, and approximately 184 K for 3. These phase transitions were also found in DSC measurements for 1 and 2. The overall magnetic behaviors for 1-3 indicate the presence of antiferromagnetic exchange interactions in the high-temperature phase and spin-gapped systems in the low-temperature phase. Below 50 K, 2 exhibits weak ferromagnetism. The spontaneous moments are nearly repressed by a field of 1.0 T. The crystal structure of 2 at 173 K reveals that there are two crystallographically independent [Pt(mnt)(2)](-) entries in an asymmetric unit. These two crystallographically independent [Pt(mnt)(2)](-) entries satisfy the spin-canting condition, and the EPR spectra measured at room temperature exhibit anisotropic character. Therefore, the weak ferromagnetic behavior in the low-temperature region for 2 can be attributed to the spin-canting phenomenon.
authors.affiliation: Coordination Chemistry Institute & State Key Laboratory and Department of Electronic Science & Engineering, Nanjing University, Nanjing 210093, People's Republic of China. x.ren@fkf.mpg.de
authors.forename: X M
authors.initials: XM
authors.lastname: Ren
authors.forename: H
authors.initials: H
authors.lastname: Okudera
authors.forename: R K
authors.initials: RK
authors.lastname: Kremer
authors.forename: Y
authors.initials: Y
authors.lastname: Song
authors.forename: C
authors.initials: C
authors.lastname: He
authors.forename: Q J
authors.initials: QJ
authors.lastname: Meng
authors.forename: P H
authors.initials: PH
authors.lastname: Wu