Multistimuli-Responsive Hydrolytically Stable “Smart” Mercury(II) Coordination Polymer

Abstract

A new one-dimensional double chain photoluminescent Hg(II) coordination polymer (CP), {[Hg(L)]·(ClO)} (1), was synthesized using a benzimidazole-appended tripodal tridentate ligand, 1,3,5-tris(benzimidazolylmethyl)benzene (L). The dynamic and flexible framework of 1 allows it to be entitled as first Hg(II)-based CP belonging to the rare category of CPs that exhibit multistimuli-responsive photoluminescence sensing properties and called as "smart" material. The sensitivity of this material via luminescence quenching method showing "turn off" behavior to a range of stimuli, including anions, solvents, and nitroaromatic compounds (NACs), offers more fine-grained control over its properties. 1 can easily adjust its channel dimensions to encapsulate different guest anions forming complete/partial anion-exchanged materials 1A-1B/1C-1E using NO, BF, OTf, OTs, and PF anions, respectively. Reversible (1A and 1B) and irreversible (1C-1E) anion exchange behaviors were observed for the complete and partial anion-exchanged products, respectively. The noteworthy feature of the anion-exchanged compounds is their anion-triggered luminescent behavior depending on different properties of anions.The excellent emission in water and high hydrolytic stability of 1 allows its use for rapid and efficient fluorescence-based detections of NACs in aquatic system. The uncoordinated pendant benzimidazole moiety in 1 serves as Lewis basic recognition site for trinitrophenol (TNP) detection, and along with electron- and energy-transfer mechanisms, 1 forms a luminescent probe for detection of TNP with low detection limits (0.55 ppm), exhibiting excellent photostability and recyclability. 1 also represents the first reported Hg(II)-based sensory CP material that can discriminate nitrophenol and nitroaniline isomers through fluorescence sensing.

Optical Sensing (Nano)Materials Based on Benzimidazole Derivatives

“…Besides conjugated polymers, benzimidazole-based materials can be developed as luminescent metal organic frameworks (MOFs) [31][32][33][34][35] or coordination polymers [36][37][38][39][40][41][42]. Such advanced functional materials have been extensively applied in the field of luminescence sensing due to their diverse structural characteristics and tunable pore sizes.…”

“…Luminescent material is the first example of Hg(II) coordination polymer with multistimuli-responsive properties ( Figure 2B). Luminescence quenching response is observed to a range of stimuli, including anions, solvents and nitroaromatic compounds [37].…”

Humidity-Induced Structural Transformation in Pseudopolymorph Coordination Polymers

“…Over the past few decades, wide research in the field of coordination polymers (CPs) has been conducted . The high potential of CPs in gas storage and separation, sensing, − catalysis, and other areas like magnetic properties , and electrical conductivity , is the main reason that this field has been of great interest among scientists and crystal engineers.…”

Metal-Organic Framework-Based Stimuli-Responsive Polymers

“…A triple responsive coordination system was reported by Tripathi et al, in which the photoluminescence of the complex can be dynamically switched by anions, solvent and nitroaromatic compounds [75]. The one-dimensional double chain coordination polymer was synthesized by a benzimidazole-appended tripodal tridentate ligand, 1,3,5-tris(benzimidazolylmethyl)benzene, and Hg 2+ as metal ions with a formula of {[Hg(L) 2 ]•(ClO 4 ) 2 } n .…”