title: Design of a magnetic bistability molecular system constructed by H-bonding and pi...pi-stacking interactions.
abstract: Crystal structures and magnetic properties were determined for two novel polymorphs of the complex [H2DABCO][Ni(mnt)2] [(H2DABCO)2+ = diprotonated 1,4-diazabicyclo[2.2.2]octane; mnt2- = maleonitriledithiolate]. For each polymorph, anions form a layered structure in which two kinds of dimers were observed. The adjacent anionic sheets are held together by cations via H-bonding interactions between protons of cations and CN groups of anions. Two polymorphs possess spin bistability; namely, upon cooling, a magnetic transition happens at around 120 K with about 1 K hysteresis on heating for the alpha phase and at 112 K with about 10 K hysteresis for the beta phase. Above the transition, the magnetic behaviors of two polymorphs can be approximately interpreted by a singlet-triplet model of an antiferromagnetically coupled S = 1/2 dimer, which is supported by the crystal structures and spin dimer analyses based on extended Hückel molecular orbital calculations.
authors.affiliation: Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan. xmren@es.hokudai.ac.jp
authors.forename: X M
authors.initials: XM
authors.lastname: Ren
authors.forename: S
authors.initials: S
authors.lastname: Nishihara
authors.forename: T
authors.initials: T
authors.lastname: Akutagawa
authors.forename: S
authors.initials: S
authors.lastname: Noro
authors.forename: T
authors.initials: T
authors.lastname: Nakamura