Supramolecular control of spin-crossover phenomena in lipophilic Fe(II)-1,2,4-triazole complexes

Keita Kuroiwa, Tomoko Shibata, Sono Sasaki, Masaaki Ohba, Atsushi Takahara, Toyoki Kunitake, Nobuo Kimizuka

Research output: Contribution to journalArticlepeer-review

52 Citations (Scopus)

Abstract

The spin-crossover properties of lipophilic, supramolecular Fe(II) complexes bridged by 4-(3-dodecyloxy)propyl-1,2,4-triazole [Fe(II)(1) 3Cl2] were investigated in chloroform and cast films. A purple low-spin (LS) complex in a powdery form was transformed into pale yellow high-spin (HS) polymers by dissolution in chloroform. The formation of lipophilic molecular wires in chloroform was observed with transmission electron microscopy. The casting of chloroform solutions onto solid supports produced purple, transparent films (LS state). The cast films exhibited sluggish spin-crossover (LS ⇌ HS) behavior without thermal hysteresis. On the other hand, the cocasting of equimolar dodecanol or tetradecanol with Fe(II)(1)3Cl2 produced composite films in which alcohol molecules were bound to the complex by ionic hydrogen bonding (ROH⋯Cl-) and van der Waals interactions. At room temperature, the cast films exhibited regular lamellar structures before and after alcohol doping; this was confirmed by wide-angle X-ray diffraction measurements. Interestingly, the Fe(II)(1)3Cl2/CnOH (n = 12 or 14) ternary films showed a reversible abrupt spin crossover accompanied by thermal hysteresis. The observed bistability was related to dynamic structural transformations between lamellar and hexagonal structures. This study provides a novel supramolecular approach to designing spin-crossover polymer films with controlled thermal bistability.

Original languageEnglish
Pages (from-to)5192-5202
Number of pages11
JournalJournal of Polymer Science, Part A: Polymer Chemistry
Volume44
Issue number17
DOIs
Publication statusPublished - Sep 1 2006

All Science Journal Classification (ASJC) codes

  • Polymers and Plastics
  • Organic Chemistry
  • Materials Chemistry

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