Synthesis And Crystal Structures Of Two Derivatives Of 2-fluoro-nicotinamide And Their Coordination Compounds

The conformation of flexible molecules is diverse and it is difficult to predict the crystal structure when synthesizing coordination polymer crystals with flexible molecules as ligands.Because intramolecular hydrogen bonding can be used to limit intramolecular rotation,we can use it to control the conformation of organic molecules.In this paper,we designed and synthesized two N-pyridinylnicotinamide derivatives that bear fluorine substituents,and used them to synthesize coordination polymer crystals.It was anticipated that intramolecular N-H···F hydrogen bonds would improve the conformational predictability of these two compounds in coordination polymer crystals.In Chapter 2,we designed and synthesized 2-fluoro-N-（pyridin-3-yl）nicotinamide（S4）,which can form an intramolecular N-H···F hydrogen bond.Six coordination polymer crystals,one coordination compound crystal and one single-component crystal were synthesized with S4 as a ligand,and the single crystal structures were analyzed.The coordination compound crystal has a two-dimensional lattice structure.Among the 6 coordination polymer crystals,one crystal has a three-dimensional lattice structure,two have a two-dimensional lattice structure,and three have a linear structure.In crystal-1 and crystal-3,pyridine N atoms at both ends of S4are coordinated with metal ions.Only the aminopyridine N atom of S4 is coordinated with metal ions in crystal-2 and crystal-4～crystal-7.Intramolecular N-H···F hydrogen bonds are formed in six crystals.Therefore,it is inferred that the intramolecular hydrogen bonding facilitates the control of the conformation of S4 molecules.In Chapter 3,we designed and synthesized 2-fluoro-N-（2-fluoropyridin-3-yl）nicotinamide（S6）,which has two fluorine substituents.A coordination polymer crystal and a single-component crystal were synthesized based on S6,and the single crystals structure were analyzed.The single-component crystal contains three S6molecules,of which two S6 molecules form strong three-center intramolecular hydrogen bonding.The metal Cd in the coordination polymer crystal adopts{Cd O₇}seven-coordination mode,and three water molecules coordinate with the metal ion.Pyridine groups of S6 molecule do not participate in the coordination,but form hydrogen bond with water molecules.This crystal has a supramolecular layer-column structure.In the two crystals,there are a total of five S6 molecules,four of which exist in a nearly planar conformation,and they all form the three-center intramolecular hydrogen bonding as expected.