Temperature dependent study on the crystal structures and physical properties of some derivates of 2,2′:6′,2′′-terpyridine chelating Co metal complexes

• Main Authors: CHEN, YAN-AN, 陳衍安
• Other Authors: HSU, I-JUI
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/z78ftw

碩士 === 國立臺北科技大學 === 分子科學與工程系有機高分子碩士班 === 107 === Developing new Spin crossover (SCO) complexes with abrupt spin transition character on terpyridine binding Co(II) complex is the main purpose of this thesis. In this work, we report some terpyridine related metal complexes [CoII(L)2][BF4]2 (L = 4'-(2-Furyl)-2,2′:6′,2′′-terpyridine (ftpy), or 1-methyl-1H-Pyrrol-2-yl-2,2′:6′,2′′-terpyridine (mtpy)). In these metal complexes, [CoII(ftpy)2][BF4]2‧1.5H2O (1) exhibits SCO behavior from HS state with μeff=3.99 B.M. at 300K to LS state with μeff= 1.88 B.M. at 100K, but [CoII(mtpy)2][BF4]2(2) only displays HS state. To resolve how structural variations related to SCO phenomenon, temperature dependent single crystal X-ray diffraction (SXRD) and temperature dependent powder X-ray diffraction (PXRD) are carried out. The result of SXRD indicate that the crystal structures are in triclinic system from 100 K(LS) to RT (HS) with averaged Co-N distance varied from 2.022(4) Å to 2.098(7) Å. The distortion indices  and  of 1 at 100 K are 88.78° and 598.49°, respectively, which are lower than those values at RT with 118.88° and 620.76°, respectively. Taking insight into crystal packing structure, one H2O is located around ~ 3.256 Å away from one of furan in complex 1, and the distance between H2O and furan increases from 3.256 Å to 3.338 Å when temperature rises from 100 K to RT. This shortening in distance indicates intermolecular interaction plays an important role in tuning SCO phenomenon in such case. In addition, the temperature dependent of x-ray absorption spectroscopy (XAS) of Co K-edge and LIII,II-edge are applied to study the electronic structures of complex 1. The results indicate that the 10Dq is about ~0.9 eV at HS state. Finally, the density functional theory (DFT) calculation is used to characterize the electronic structure and chemical bonding between HS and LS.