Syntheses And Properties Of Hybrids Based On 2,4,6-Tri(2-Pyridyl)-1,3,5-Triazine Zinc Halide

Electron donor-acceptor hybrid materials have attracted much attention because of their tunable composition,structure and bandgap,as well as their wide range of applications in data storage,optical switching,decoration,display and nonlinear optics.In recent years,organic-inorganic hybrid photochromic materials consisting of electron donors and acceptors have been widely studied.Organic electron acceptors are mainly pyridyl ligands,especially for 4,4'-bipyridine and its derivative.However,4,4'-bipyridine and its derivatives have relatively few coordination sites,relatively weak coordination capabilities and relatively simple coordination modes,which have restricted the structural and functional diversity of hybrid materials to some certain extent.Therefore,the rational selection of organic ligands with multiple coordination sites and coordination modes as electron acceptors has become the key factor for constructing photochromic electron donor-acceptor hybrid systems.2-TPT(2,4,6-tri(2-pyridyl)-1,3,5-triazine)is a polydentate chelating ligand with strong coordination ability and multiple coordination groups as well as coordination mode.It is widely used to construct coordination polymer materials with various structures and excellent properties,such as photomagnetism,photocatalysis and photoluminescence.In addition,2-TPT possesses a large?conjugated system with a triazine ring and three pyridine rings,which has a very large positive quadrupole moment and a very strong polarizability.It is an excellent electron-deficient acceptor,which can match with strong Lewis bases to construct a photochromic material with excellent performance.Metal halides are ideal components for constructing organic-inorganic hybrids composed of electron donor-acceptor due to the rich skeleton structure and excellent semiconductor characteristics.Their electron donating ability can be adjusted in a wide range with the change of the metal and halogen connecting mode accompanying the degree of aggregation.Based on the above consideration,by using solvent evaporation method at room temperature,ten 2-TPT-based zinc halide hybrids have been designed and synthesized through introducting the electron acceptor 2-TPT with multiple coordination modes and excellent electron-deficient abilities into electron-rich zinc halide system.The electron deficiencies of the electron acceptors,the electron donating abilities of the electron donors and the hybridization modes of the hybrids have been systematically modulated to explore the electron donor-acceptor relationship matching,interfacial relationship matching,photoinduced electron transfer behaviors and photochromic mechanism in the electron donor-acceptor system.Through structural analysis and property characterization,it was found that:(1)2-TPT as a strong electron acceptor can match with strong Lewis bases(Cl~-/Br~-)to construct hybrid materials composed of electron donor and acceptor,which exhibit excellent photoluminescent and photochromic properties.However,2-TPT cannot match with weak Lewis base(I~-)due to the heavy atom effect.(2)Electron-rich benzyl alcohol solvent molecules could be introduced into the complex lattice due to space filling and strong lone pair-?interactions.Furthermore,they can also play the roles of second electron donors to effectively modulate the photochromic and photoluminescence properties of the electron donor-acceptor system.(3)The single-crystal-to-single-crystal transformation could be achieved upon alternating removing lattice molecules of benzyl alcohol by heating,and placing the complex without solvent in the benzyl alcohol vapor environment.And it is an effective strategy for modulating photo-induced intermolecular electron transfer and photochromic properties by desorption and adsorption of lattice solvent molecules.(4)The effect of coordination or/and N-protonation can effectively regulate the spatial charge distribution and the electron-accepting abilities of 2-TPT,which could affect the degree of matching with potential electron donors(halogen or electron-rich solvents),and then influence photo-induced intermolecular electron transfer and photochromic properties of the electron donor-acceptor system.(5)The interfacial relationship between electron donors and acceptors is a key factor for determining that the electron donor-acceptor hybrids could undergo photo-induced intermolecular electron transfer and photochromism.Meanwhile,the lone pair-?interactions between the potential electron donors and the electron-deficient cores can act as an effective electron transfer pathway for the electron donor-acceptor hybrids.