Four new cobalt(ii) coordination complexes: thermochromic switchable behavior in the process of dehydration and rehydration

• Published in: CrystEngComm Vol. 14; no. 9; pp. 3189 - 3198
• Main Authors: Shen, Chaojun, Sheng, Tianlu, Zhu, Qilong, Hu, Shengmin, Wu, Xintao
• Format: Journal Article
• Language: English
• Published: 01.01.2012
• Subjects: Diffraction; Ligands; Magnetic measurement; Networks; Switching theory; Three dimensional; Two dimensional; X-rays
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/c2ce06478b

Four cobalt(ii) coordination complexes, {[Co sub(11)(L1) sub(6)(HL1) sub(2)(H sub(2)O) sub(28)].12H sub(2)O} sub(n) (1), [Co sub(4)(H sub(2)L1) sub( 4)(HL1) sub(2)(H sub(2) O) sub(8)].2H sub(3)L1.2H sub(2)O (2), {[Co(H sub(2)L3)(H sub(2)O) sub(3)].2H sub(2)O} sub(n) (3) and [Co(HL1)(4,4'-bpy)(H sub(2)O) sub(2)] sub(n) (4), (H sub(3)L1 = 2,4,6-tri(3-carboxyphenylthio)-1,3,5-triazine, H sub(4)L3 = 2,4-bis(3-carboxyphenylthio)-6-(4-carboxyphenylamino -1,3,5-triazine, 4,4'-bpy = 4,4'-bipyridine), was synthesized hydrothermally and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR, thermal analysis, UV-vis spectroscopy and magnetic measurements. Complex 1 shows a 2D layer structure composed of three types of secondary building units (SBUs), [M sub(1)], [M sub(3)] and [M sub(4)] bridged by [HL1] super(2-) and [L1] super(3-) linkers. While complex 2 is a tetranuclear compound and further forms a 3D supramolecular network structure based on eight types of hydrogen-bonding interactions between the molecules. The 2D framework of complex 3 can be described as 1D infinite chains interconnected by [H sub(2)L3] super(2-) ligands. Furthermore, the hydrogen-bonding interactions between the adjacent layers along the acplane makes the 2D layer structure extend to a 3D network. The structure of complex 4 can be illustrated as a 1D zigzag infinite chain with 4,4'-bipyridine as the secondary ligand. Additionally, the pi ... pi stacking interactions can be observed between the adjacent chains. An aquo-accessible thermochromic change in complexes 1-4 was induced by means of the reversible dehydration and rehydration of the crystals. Magnetic measurements showed antiferromagnetic coupling between the Co super(2+) ions in all of the four complexes.