Stimuli-Responsive Zinc (II) Coordination Polymers: A Novel Platform for Supramolecular Chromic Smart Tools

Abstract

The unique role of the zinc (II) cation prompted us to cut a cross-section of the large and complex topic of the stimuli-responsive coordination polymers (CPs). Due to its flexible coordination environment and geometries, easiness of coordination–decoordination equilibria, “optically innocent” ability to “clip” the ligands in emissive architectures, non-toxicity and sustainability, the zinc (II) cation is a good candidate for building supramolecular smart tools. The review summarizes the recent achievements of zinc-based CPs as stimuli-responsive materials able to provide a chromic response. An overview of the past five years has been organised, encompassing 1, 2 and 3D responsive zinc-based CPs; specifically zinc-based metallorganic frameworks and zinc-based nanosized polymeric probes. The most relevant examples were collected following a consequential and progressive approach, referring to the structure–responsiveness relationship, the sensing mechanisms, the analytes and/or parameters detected. Finally, applications of highly bioengineered Zn-CPs for advanced imaging technique have been discussed.

Zinc(II) Carboxylate Coordination Polymers with Versatile Applications

“…Luminescence of Zn(II)-CBCPs arises from the characteristics of the supplementary organic fluorescent ligands, such as an aromatic conjugated system, while small guest molecules can either enhance or quench this phenomenon. The origin of the luminescence in such species can be related to one or several electron transfer mechanisms, such as intra-ligand (IL), ligand-to-ligand (LLCT), and metal-to-ligand (MLCT) charge transfers [ 10 , 11 ].…”

“…Based on the good Lewis acid activity observed in living systems, this ion has found applications in several catalytic processes [ 7 ] and in developing species with biological activity [ 5 , 8 , 9 ]. Moreover, its structural control through coordination generates valuable applications as sensors based on luminescent properties for species with proper selected ligands [ 10 , 11 , 12 ]. Its stereochemical versatility also allows a structural arrangement in the complex’s network that generates pores and, thus, induces the ability of some materials to storage gaseous, liquid or solid species [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”

Recent Developments in Stimuli Responsive Smart Materials and Applications: An Overview

“…Pressure, pH, temperature, as well as electric and magnetic forces, may all be detected by smart materials. Combining NiTi alloys in a certain ratio results in a "smart material," which has the properties of a smart alloy [30][31][32][33]. The biomedical, aerospace, automotive, and electrical and electronic sectors can all benefit from the usage of NiTi alloys.…”

Role of the Environment Polarity on the Photophysical Properties of Mesogenic Hetero-Polymetallic Complexes

“…Emissive materials containing cheap biocompatible and bioavailable d -block metals like copper and zinc are considered promising in several applications, such as in optoelectronic devices [ 1 , 2 , 3 ], sensing [ 4 , 5 , 6 ], multi-stimuli responsive materials [ 7 , 8 , 9 , 10 , 11 ] and so on. The interest arises from the possibility of harvesting triplet excited states resulting in an exponential increase in emissions when compared with organic low-molecular-weight luminophores.…”