Aromatic Guest Incorporation in Naphthalene-Based Cyclotetrabenzil Host

Naphthalene-based cyclotetrabenzil octaketone is among the derivatives of cyclobenzoins which belong to the class of porous molecular crystals (PMCs), an emerging class of porous solids. These macrocycles show promise as supramolecular hosts which can include guest molecules within their pores and stabilize them by non-covalent interactions. Introduction of electron-rich aromatic compounds to similar macrocycles have provided insight into their applications in gas separation and sequestration, and organic optoelectronic devices. The macrocycle’s affinity towards chlorinated guests has since prompted attempts for co-crystallization of the macrocycle with different chlorinated guests for applications in chemical sensing of toxic contaminants including toxic and persistent aromatic polychlorinated biphenyl (PCBs). Single crystals of complexes of the octaketone with methoxybenzene (1) and 1,3-dichlorobenzene (2) were successfully grown, and their structures were solved. Single crystals of the octaketone with chloroform (3) were also obtained. Study of the single crystal structures show hydrogen bonding between the oxygen atoms of the octaketone and hydrogens of the naphthalene groups and vice-versa. Guest molecules in structures 2 and 3 also hydrogen bond to the host, but with additional chlorine atoms acting as hydrogen bond donors, further stabilizing the guest molecules towards the center of the macrocycle. Additionally, [π ···π] and [Cl···π] interactions are also observed in complexes with 2 and 3, respectively. Collectively, these interactions create a staggered stacking pattern but can hopefully form channels with varying substituents or expansion of the aromatic guest molecules. ***This project was completed with contributions from Thamon Puangsamlee from NANOTEC, Thailand.