Cocrystal Growth Of Bisimidazole Compounds And Olid-stte Photo-cycloaddition Reactions

The term of crystal engineering was used by Schmidt in 1971 for the first time.During the next decades, significant progress has been made toward the design and application of uniquely engineered crystals. Pyridine and its derivatives are often used ashydrogen-bonding/halogen-bondingacceptors in crystal engineering. Desiraju’s group prepared a lot of cocrystals containing pyridine derivatives by designing some supramolecular synthons. MacGillivary’sgroup reportedpreparation of cocrystals of pyridine derivatives as hydrogen-bonding acceptor with template molecules. Such cocrystals could undergo a [2+2] cycloadditionunder irradiation of UV light. As hydrogen-bonding/halogen-bonding acceptors, imidazole derivatives play asimilar role with pyridinederivatives. In this dissertation, bisimidazole compoundswere chosen to prepare supramolecular crystals as hydrogen-bonding/halogen-bonding acceptors through crystal engineering. Based on their crystal structures,we analysed the features of imidazole derivatives for crystal engineering. Furthermore, the crystals that meet Schmidt’s topochemical postulate were irradiated with UV light. It was studied how wavelength and the arrangement of reactive molecules in the crystalaffected the molecular structureof products.In the second chapter, we prepared 1,4-di(1H-imidazol-1-yl)benzene (DIB). 4,4’-Biphenol, terephthalic acid, isophthalic acid and succinic acid were selected as suitable candidates to investigate DIB’s ability to form hydrogenbond.DIBwas used as a halogen-bonding donor.Eight supramolecular crystals wereobtained. The DIB existed in the trans-conformation in the majority of the crystals. One-dimensional infinite chains were formed through hydrogen bonding or halogen bonding interactions. The hydrogen atoms of the imidazole ring could form C-H---X hydrogen bonding to give R21(7),R1{1) and R44(10) motifs, which could play an important role in stabilizing the crystals.In the third chapter, we prepared a cocrystal of (1E,3E)-1,4-di(1H-imidazol-1-yl)buta-1,3-diene (DIBD) with 5-methoxyresorcinol. Each two DIBD molecules and two 5-methoxyresorcinolmolecules constitute a four-molecule unit. In this unit, the double bonds of DIBD molecules meet Schmidt’s topochemical postulate for solid-state cycloaddition. DIBD molecules in the cocrystal were irradiated with 313.5 nm light to produce a 1,2-divinyl-cyclobutane derivativethrough a [2+2] cycloaddition reaction. When being heatedat 150℃,this dimer underwent a Cope rearrangementto produce a second dimer, a cyclooctadiene derivative.This cyclooctadiene derivativewas obtained by irradiating the cocrystal with a Hg lamp without an optical filter. It was found that 257 nm light is critical for the formation of cyclooctadiene derivative. The dependence of thephotochemical products on the light wavelength may originate in the characteristic UV absorption for these systems.In the fourth chapter, five new cocrystals wereprepared via hydrogen-bonding and halogen-bonding, including the cocrystal of DIBDand resorcinolas well as the cocrystal of DIBD and4,4’-biphenol. The former one is composed of four-molecule units, whereas the later one, 1D infinite chains.The cocrystal of DIBD with biphenolunderwent a [2+2] cycloaddition under the irradiation of a Hg lamp without an optical filter with a yield of50%. In this cocrystal, there are two kinds of possible reaction routes among the double bonds of DIBD molecules. The double bond chose to react with the closer one to give a 1,3-divinyl-cyclobutane derivative.The range of hydrogen-bonding acceptors in a cocrystal was extended from the commonly used pyridine derivatives to imidazole derivatives, thus providing additional options for future crystal engineering and molecular design for solid-state cycloaddition. Based on the results of chapter 3 and chapter 4, the DIBD’s arrangement in cocrystals determined the products’structure. Through crystal engineering, the same compound canform different molecular arrangement, and people could efficientlyobtainmultiple cycloaddition products separately.