An organometallic half-sandwich supramolecular complex {K(18-Crown-6)(ηn-C6H5B(C6H5)3)} (n = 1-6) exhibiting a reversible breaking-symmetry phase transition and switchable dielectric behaviour

Guo-Jun Yuan; Dong-Sheng Shao; Zhi-Yuan Yao; Wen-Long Liu; Xiao-Ming Ren

doi:10.1039/c8dt04060e

An organometallic half-sandwich supramolecular complex {K(18-Crown-6)(ηⁿ-C₆H₅B(C₆H₅)₃)} (n = 1-6) exhibiting a reversible breaking-symmetry phase transition and switchable dielectric behaviour

Dalton Trans. 2018 Dec 21;47(47):16835-16839. doi: 10.1039/c8dt04060e. Epub 2018 Nov 12.

Authors

Guo-Jun Yuan¹, Dong-Sheng Shao², Zhi-Yuan Yao³, Wen-Long Liu⁴, Xiao-Ming Ren²

Affiliations

¹ Key Laboratory of Advanced Functional Materials of Nanjing, Department of Chemistry, Nanjing Xiaozhuang University, Nanjing 211171, P. R. China. ahchljygj@163.com and State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 210009, P. R. China. xmren@njtech.edu.cn and Department of Chemistry, University of California, Riverside, California 92521, USA.
² State Key Laboratory of Materials-Oriented Chemical Engineering and College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 210009, P. R. China. xmren@njtech.edu.cn.
³ Key Laboratory of Advanced Functional Materials of Nanjing, Department of Chemistry, Nanjing Xiaozhuang University, Nanjing 211171, P. R. China. ahchljygj@163.com.
⁴ College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, P. R. China.

PMID: 30417182
DOI: 10.1039/c8dt04060e

Abstract

A supramolecular crystal, built from a 1 : 1 molar ratio of potassium tetraphenylboron (KBPh₄) with 1,4,7,10,13,16-hexaoxacyclooctadecane (18-Crown-6), contains an organometallic half-sandwich superstructure unit {K(18-Crown-6)(ηⁿ-C₆H₅B(C₆H₅)₃)} (1 with n = 1-6), and shows a reversible phase transition at ∼211 K. The analysis of crystal structures at 173 K in the low-temperature phase, and 293 and 423 K in the high-temperature phase revealed that the breaking-symmetry phase transition is associated with the order-disorder transformation of [K(18-Crown-6)]⁺ and the change of the coordination mode of the phenyl ring to K⁺. A dielectric anomaly appears at ca. 212 K and dielectric relaxation occurs above 375 K in 1. The dielectric and thermal anomaly temperatures are close to each other, and the dielectric relaxation is relevant to the relative displacement of [K(18-Crown-6)]⁺ and the tetraphenylboron anion.