Structural, mesomorphic, photoluminescence and thermoelectric studies of mononuclear and polymeric complexes of copper( ii ) with 2-hexyldecanoato and 4,4′-bipyridine ligands

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2015-01, Vol.3 (42), p.11036-11045
• Main Authors: Abdullah, Norbani, Hashim, Rauzah, Ozair, Lailatun Nazirah, Al-Hakem, Yasameen, Samsudin, Habibah, Marlina, Anita, Salim, Malinda, Mohd. Said, Suhana, Subramanian, Balamurugan, Nordin, Abdul Rahman
• Format: Article
• Language: English
• Subjects: Binding; Charge transfer; Chelating; Columns (structural); Cooling; LIGANDS; LUMINESCENCE; Molecular structure; Photoluminescence; POLYMERS; SINGLE CRYSTALS; THERMAL STABILITY; Thermoelectricity
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C5TC02273H

[Cu(R) 2 (bpy) 2 ]·2RH ( 1 ) and [Cu 2 (R) 4 (bpy)] x ( 2 ) were obtained from the reaction of [Cu 2 (R) 4 (RH) 2 ] (R = 2-hexyldecanoato) with 4,4′-bipyridine (bpy) using different work-up procedures. Complex 1 consisted of single crystals and its molecular structure showed a distorted octahedral Cu( ii ) with two chelating bidentate R. Complex 2 has a similar structure as crystals of a linear-chain coordination polymer, [Cu 2 (CH 3 (CH 2 ) 5 COO) 4 (bpy)] x ( 3 ). Both 1 and 2 were thermally stable ( T dec = 240 °C for 1 ; 220 °C for 2 ), have low melting temperatures ( T m = 52.3 °C for 1 ; T m = 48.3 °C for 2 ) and exhibited temperature-dependent mesomorphisms. For 1 , the mesomorphism arose from the change in the binding mode of R from chelating to bridging during isotropization, while for 2 , the mesomorphism arose from the breaking of the Cu–N bpy bonds. The mesophases for 2 were cubic columnar (Cub, P 4 3 32) and rectangular columnar (Col R , space group p 2 gg ) on cooling from 150 °C, Cub and hexagonal columnar (Col H ) on cooling from 184 °C (isotropic liquid phase), and Col H and nematic columnar (Col N ) on cooling from 190 °C. These complexes also exhibited photoluminescence upon charge transfer and d – d excitation. Finally, the Seebeck coefficient value ( S e ) for 2 was −0.47 mV K −1 , identifying it as a potential thermoelectric material.