Tamas Holczbauer, as Inviting Lecturer, took part at the 43rd International Conference on Coordination Chemistry in Sendai, Japan and visited the Laboratorium of Prof. Masaki Kawano at the Tokyo Institute of Technology.
Co-authors: L. Bereczki, N.V. May, D.V. Horváth, R. Palkó, T. Soós, P. Bombicz
Title: New porous frameworks assisted by hydrogen and halogen bonds
The discovery of the metal organic frameworks (MOFs) has opened a new branch of research two decades ago. The covalent organic frameworks (COFs) were synthesized in the 2000’s. Highly porous hydrogen-bond assisted organic frameworks (HOF) were first reported a decade ago. Intermolecular forces and molecular inflexibility are the conditions of the formation of non-covalently bonded organic frameworks. Most of the published organic frameworks (MOFs and COFs) are electronically neutral, but some of them are ionic (iMOFs and iCOFs). The first iHOF is reported now.
Three different polymorphic- and solvatomorphic iHOF frameworks1 of the investigated molecule (1: 5,5,11,11-tetrabutyl-1,3,7,9-tetraphenyl-4,5,6,10,11,12-hexahydro-5,11- diazadibenzo[ef,kl]heptalene-5,11-diium-bromide) were prepared by using different crystallization techniques and were structurally characterized using single crystal X-ray diffraction technique. Crystals of 1a were obtained by recrystallization of 1 from THF solution in the presence of the solid powder. 1a crystallizes in space group Fddd and almost the half of the unit cell (42%) was found to be filled with disordered THF solvent molecules. Crystals of 1b were grown by slow evaporation of THF, the dimorphic structure has the Pnna space group. In this case the void volume is ~39% per unit cell. The crystals of 1c were received by fast evaporation of the solvent mixture of THF and pyridine. The molecules crystallize in the P21/n space group and contain voids of ~18% where the pyridine molecules take part in the framework construction as neutral linkers.
The frameworks of 1a and 1b are polymorphs, while 1a/1b and 1c are solvatomorph frameworks. The solvent THF molecules are disordered throughout the channels. The framework is held together by charge assisted H-bonds and Br-…π interactions.