Clathrates of novel ethylenediamine derivatives: thermal, X-ray crystallographic and conformational analysis of inclusion complexes of N,N′-bis(5-phenyl-5-dibenzo[a,d]cycloheptenyl)ethylenediamine and its 10,11-dihydro analogue

Abstract

Novel compounds N,N′-bis(5-phenyl-10,11-dihydro-5-dibenzo[a,d]cycloheptenyl)ethylenediamine 3a and N,N′-bis(5-phenyl-5-dibenzo[a,d]cycloheptenyl)ethylenediamine 3b are efficient hosts, forming clathrates upon recrystallization from a wide variety of organic solvents. The 1:2 and 1:1 complexes of 3a and 3b, respectively, with dichloromethane, dibromomethane and diiodomethane were subjected to extensive thermal and X-ray crystallographic studies, and it was found that guests of the thermally less stable complexes reside in channels, while these are accommodated in discrete cavities in the more stable complexes. Host 3a adopts similar conformations in its complexes with CH2Cl2 and CH2Br2, while a different conformer is involved with CH2I2. DFT (B3LYP/6-31G*) geometry optimizations revealed that these conformers are respectively, 8.7 and 7.5 kJ mol−1 less stable than the global minimum energy conformer of 3a. Host 3b adopts similar conformations in its three complexes, which optimize to the global minimum energy conformer. In the thermally more stable complexes, 3a and 3b exist as relatively low energy conformers.