Preparation Of Low Weight Molecular Gels Containing Pyridinyl And Their Response To CO Or Pd²⁺

Low weight molecular gels（LMWGs）is a new smart soft material with sensing and adapting to a variety of external stimuli（such as temperature,acid and base,mechanical force,light irradiation,etc.）.In this paper,two series of gel factors with pyridine group as the main structural unit were designed and synthesized,and their properties were explored.We designed and synthesized A series of gel factors,which can realize visual recognition and detection of CO through Pd²⁺coordination.Series A gel factor is a tripod structure consisting of phloroglucinol,flexible alkyl chains and pyridine groups.Among them,phloroglucinol is the core part,alkyl chains are the linking parts and pyridine groups are the coordination groups.They can cooperate with Pd²⁺as a CO response recognition unit.Series A formed one-dimensional fiber structure through hydrogen bonding,Ï€-Ï€packing and other forces firstly,and then formed crosslinking network through the coordination between pyridine and palladium acetate,encapsulating solvent to form small molecular gel.The rheological experiments on the gels of Series A compounds show that they have preferable gel properties.When the A-series gel was placed in CO atmosphere for 15 min,both A1 and A2 gel showed collapse to a certain degree.The collapse of A2 with longer carbon chain exhibited more obvious.On the other hand,we designed and synthesized B series of gel factors,aiming at the detection of Pd²⁺by using the fluorescence properties of naphthalimide and the coordination between Pd²⁺and pyridine.B series gel factors are composed of naphthalimide as fluorescence group and pyridine group as Pd²⁺response group.Rheological experiments show that B series has good gel properties.The driving force of formation of B series gels was characterized by infrared spectroscopy.The quantitative experiments on the response of B series compounds to Pd²⁺in solution state show that B series compounds have excellent ion selectivity and anti-interference to Pd²⁺.The B series compounds were characterized by ¹H NMR,which indicated that Pd²⁺had completed the coordination with pyridine.Taking B3 compound as an example,the response behavior of the gel to Pd²⁺was explored.After adding Pd²⁺,the gel showed collapse phenomenon and fluorescence quenching effect.