Preparation and structures of novel [2.2.2]metacyclophane tweezers

Abstract

[2.2.2]Metacyclophane (MCP) tweezers 7 and azo[2.2.2]MCP tweezers 8 were prepared from 21-nitro[2.2.2]MCP 2, which was obtained by the ipso-nitration of [2.2.2]MCP 1. X-Ray crystal structural analysis shows the MCP tweezers 7 to have the anti-conformation. The photothermal isomerization of azo[2.2.2]MCP tweezers 8 was studied by UV spectroscopy, and the activation energy of the thermal cis–trans isomerization was determined by UV measurements at variable temperatures to be E^‡ = 71 ± 7 kJ mol⁻¹. The complexation constant of 8 with silver ions was determined by the Benesi–Hildebrand method to be 73 ± 3 L mol⁻¹.