다공성 배위화합물과 X선 관찰을 통한 불안정한 황, 인 동소체의 선택적 포획과 반응성 연구

Abstract

This thesis describes the study of selective capture of labile sulfur allotropes and elucidation of their chemistry, from abundant, stable sulfur element by gas-phase diffusion to a thermally stable porous coordination network (PCN). The thesis also presents a simple way to stabilize reactive phosphorus allotropes by gas phase diffusion into a PCN, and the development of a potentially-useful molecular container as a reagent source. Chapter 1 is a brief summary of development of PCNs, application of PCN as a functional molecular flask, and chemistry of small allotrope sulfur (Sn, n < 6) and white phosphorus (P4). PCNs are composed of metal and organic building block that can be modified; they have been developed for many applications including gas separation, gas absorption, and heterogeneous catalysis. The robustness and crystallinity of PCNs enables guest encapsulation and observation of molecular structure by X-ray diffraction. Moreover, unique pore environments, such as -planes, halogens, and open metal sites, provide interactive space for selective capture of molecules. Those properties of PCNs enable selective trapping and observation of reactive species. The structure and property of small allotropes of sulfur has not been studied because of their instability. White phosphorus is a reactive, useful reagent, but because of auto ignition in air, the chemistry of suboxide phosphorus (P4Ox, x < 6) was unknown, and simple utilizations have not been developed. In this chapter, the potential of PCN as a molecular flask for labile sulfur allotropes and reactive white phosphorus will be presented. Chapter 2 describes a method to selectively trap small allotropes, analysis of structure by powder X-ray diffraction, and the mechanism of interconversion reaction of allotropes in the pore of a PCN. For the first time, trisulfur (S3) was stabilized as a neutral state, and the structure was determined using crystallography. The halogen-sulfur interaction had an important function in the selective capture and stabilization of the small sulfur molecules. Catalytic, mechanical, and photo chemical stimuli induced interconversion reactions between S3 and S6 in the pore. Chapter 3 demonstrates an easy method to stabilize reactive P4 by gas phase diffusion from red phosphorus, extraction of P4 by solvent exchange and heating, and potentials of P4@PCN as a reagent source for reactions. The thermal stability of network enabled direct heating of network and red phosphorus at 673 K, and result in high yield (ca. 93 % occupancy in pore) of P4 trapping. Due to the chemical and thermal stability of the PCN, P4 could be extracted and the network could be regenerated.