Research On Construction And Properties Of Functional Acylhydrazone Polynuclear Complexes

Acylhydrazone Schiff base is a kind of multidentated chelate ligands to coordinate with metal ions.The acylhydrazone group itself is rich in electrons,which is beneficial to the design of diverse structures and the realization of specific functional properties.Therefore,it is very meaningful for us to explore the coordination regularity of acylhydrazone ligands with metal ions so that we can realize the controllable synthesis of functional complexes of acylhydrazone Schiff base.In this work,twenty transition or rare earth metal complexes based on a series of monoacylhydrazone,bisacylhydrazone and triacylhydrazone Schiff base ligands with different functional groups have been synthesized.These complexes were characterized by FT-IR,elemental analysis,TGA,UV-vis,FL spectra,NMR spectra,Mass spectra,XRPD,and single crystal X-ray diffractions.The coordination regularity and the relationship between structure and properties were discussed in detail.The research results are as follows:1.Based on previous work by our group,four monoacylhydrazone Schiff base ligands,namely H₃L¹,H₄L²,H₂L³ and H₂L⁴ with different substituents were prepared,and their coordination complexes of Cu（Ⅱ）,Cd（Ⅱ）,Zn（Ⅱ）,Y（Ⅲ）,and Dy（Ⅲ）have been synthesized.[Cu₂（HL¹）₂（CH₃OH）₂]·2CH₃OH（1）[Cd₂（H₂L¹）₂（Ac）₂（DMF）₂]（2）（H₃L¹=（E）-4-hydroxy-N’-（2-hydroxy-5-nitrobenzylidene）benzohydrazide）[Y₃（H₂L²）₂（Ac）₄（HAc）（CH₃OH）₂（H₂O）]·[Y₃（H₂L²）₂（Ac）₆（CH₃OH）（H₂O）]·5H₂O（3）[Dy₃（H₂L²）₂（Ac）₄（HAc）（CH₃OH）₂（H₂O）]·[Dy₃（H₂L²）₂（Ac）₆（CH₃OH）（H₂O）]（4）（H₄L²=（E）-N’-（2,3-dihydroxybenzylidene）-4-hydroxy-3-methoxybenzohydrazide）[Cd₂（HL³）₂（CH₃OH）₄]·2NO₃（5）（H₂L³=（E）-N’-（2-hydroxy-3-methoxybenzylidene）-2-（4-nitrophenoxy）acetohydrazide）[Zn₂（L⁴）₂（CH₃OH）₂]（6）[Y₂（HL⁴）₂（Ac）₄（H₂O）₂]·CH₃OH（7）[Dy₂（HL⁴）₂（Ac）₄（CH₃OH）₂]·CH₃OH（8）（H₂L⁴=（E）-N’-（（2-hydroxynaphthalen-1-yl）methylene）-2-（4-nitrophenoxy）acetohydrazide）Complexes 1 and 2 are binuclear complexes and the ligand in 1 and 2 were presented as enol and keto structures,respectively.Complexes 3 and 4 are iso-structural trinuclear coordination complexes with central metal of Y for 3 and Dy for 4.Complex 5 is a binuclear Cd complex,which has emission with maxima at 478 nm in its solid fluorescent spectra and the red-shift relative to that of the ligand.The complexes 6,7 and 8 are the binuclear complexes of Zn,Y and Dy,respectively.The ligand in 6 presented as enol conformation,and the asymmetric units are bridged by oxygen atoms of phenolic hydroxyl groups,while 7 and 8 are both bridged by acetic oxygen atoms.Due to the introduction of naphthalene ring into the ligand,the aromaticity is enhanced,therefore,the strongπ-πstacking interactions were observed in 6 and 7.2.Four bisacylhydrazone Schiff base ligands H₆L⁵,H₄L⁶,H₄L⁷ and H₄L⁸ with different substituents were prepared through selecting succinic acid and isophthalic acid hydrazide as reactants,and the Zn（Ⅱ）and Cd（Ⅱ）complexes with these ligands have been synthesized.[Zn₂（H₄L⁵）₂]·2CH₃OH·H₂O（9）（H₆L⁵=（N’¹E,N’⁴E）-N’¹,N’⁴-bis（2,5-dihydroxybenzylidene）succinohydrazide）[Zn₂（H₂L⁶）₂]·5DMF（10）[Cd₂（H₂L⁶）₂]·DMF·H₂O（11）（H₄L⁶=（N’¹E,N’⁴E）-N’¹,N’⁴-bis（2-hydroxy-5-nitrobenzylidene）succinohydrazide）[Zn₂（H₂L⁷）₂]·3H₂O（12）（H₄L⁷=（N’¹E,N’⁴E）-N’¹,N’⁴-bis（5-chloro-2-hydroxybenzylidene）succinohydrazide）[Zn₄（H₂L⁸）₄]·CH₃OH·H₂O（13）（H₄L⁸=（N’¹E,N’³E）-N’¹,N’³-bis（2-hydroxy-3-methoxybenzylidene）isophthalohydrazide）Complex 9 is a binuclear Zn complex.Its luminescent property in methanol has been investigated.The emission maximum exhibits at 526 nm,which is red-shifted with respect to the free ligand.Complexes 10 and 11 are also binuclear complexes of Zn and Cd,respectively,the molecular structure of which are both similar to 9,shaped as butterfly.Complex 12 is a Zn complex with ligand H₄L⁷.Although no crystals were obtained,we have proposed that the structure of 12 through the Job’s-plot curve and NMR titration,combined with elemental analysis and thermogravimetric analysis,which is similar to structures of 9-11 and contains three free water molecules.The solid luminescent property of 12 has shown a strong emission at 494 nm and blue-shift.In methanol solution,the complex 12 has a fluorescent emission at 471 nm and 15 nm red-shift.Although the complexes 9-12 have similar structures,they have different luminescent properties due to the different functional groups at the 5-position of the salicylaldehyde moiety.The ligand H₄L⁸ was obtained by introducing the benzene ring to the bisacylhydrazone Schiff base ligand,which displays a relatively large and planar tetranuclear well shaped molecular square 13 with nearly linear configuration.3.The three triacylhydrazone Schiff base ligands H₉L⁹,H₆L¹⁰ and H₆L¹¹ with C₃symmetries were successfully prepared through synthesizing 1,3,5-benzenohydrazide as the precursor.The Zn（Ⅱ）,Y（Ⅲ）,Dy（Ⅲ）,Eu（Ⅲ）,La（Ⅲ）and Tb（Ⅲ）coordination complexes with these ligands have been synthesized.{[Zn（H₇L⁹）]·2H₂O}_n（14）（H₉L⁹=（N’¹E,N’³E,N’⁵E）-N’¹,N’³,N’⁵-tris（2,3-dihydroxybenzylidene）benzene-1,3,5-tricarbohydrazide）[Zn₃(H₃L¹⁰)（Ac）₃（H₂O）₃]·3H₂O（15）(H₆L¹⁰=（N’¹E,N’³E,N’⁵E）-N’¹,N’³,N’⁵-tris（（2-hydroxynaphthalen-1-yl）methylene）benzene-1,3,5-tricarbohydrazide)[Y₄(H₂L¹¹)₃（DMF）₃（H₂O）₃]·21DMF·H₂O（16）[Dy₄(H₂L¹¹)₃（DMF）₃（H₂O）₃]·11DMF·H₂O（17）[Eu₄(H₂L¹¹)₃（DMF）₃（H₂O）₃]·4DMF·H₂O（18）[La₄(H₃L¹¹)₄]·12DMF·2CH₃OH·3H₂O（19）[Tb₄(H₃L¹¹)₄]·7DMF·2CH₃OH·4H₂O（20）(H₆L¹¹=（N’¹E,N’³E,N’⁵E）-N’¹,N’³,N’⁵-tris（2-hydroxy-5-nitrobenzylidene）benzene-1,3,5-tricarbohydrazide)Complex 14 is a Zn complex feature 1D chain structure,in which two types of chiral chains crystallize in pairs,leading to a racemic product.Complex 15 is a trinuclear Zn complex with a three-leaf fan-like molecular structure in which the three binding pockets of the ligand are coordinated with three Zn ions,respectively.The acetate and water molecules occupy the remaining metal coordination sites,the methyl peak of the acetate can be seen from ¹H NMR spectra clearly.The solid luminescent property of 15 exhibits strong emission at 580 nm.In DMF solution,its fluorenscent emission is red-shift and the intensity is increased significantly compared with that of the ligand.It can be seen that the complex 15 has preferable luminescent property.The complexes 16,17 and 18 are structurally analogous tetranuclear complexes of Y,Dy and Eu,respectively.The three complexes exhibit tetrahedral cage-like structure with the bottom opening,in which the four metal ions in the structure have the different coordination environment.The chemical environment of the three arms of the ligand in the structure is also different,one of the arm of the acylhydrazone group is presented as enol structure,which led to the formation of the neutral[M₄(H₂L¹¹)₃（DMF）₃（H₂O）₃]tetrahedral cage.Complexes 19 and 20 are structurally analogous tetranuclear cage-like structure complexes of La and Tb,respectively.Unlike16-18,the four metal ions in the structure have the same coordination environment and the chemical environment of the three arms of the ligand is also same.Each negative trivalent ligand bridgs three metal ion centers,which led to the formation of the neutral tetrahedral cage structure[M₄(H₃L¹¹)₄].The coordination regularity of acylhydrazone ligands,controllable synthesis,supramolecular assembly and the fluorescence properties of acylhydrazone complexes are studied systematically in this work based on the interaction of monoacylhydrazone,bisacylhydrazone and triacylhydrazone Schiff base ligands with the transition and rare earth metals.Twenty functional complexes with novel structures have been obtained through the design of ligands and the regulation of synthesis conditions such as metal ions and solvents.The structures and fluorescence properties of these complexes were analyzed and discussed from the point of view on the issues such as the structural characteristics of ligands,the functional groups,the sizes and coordination numbers of metal ions and the bridging function of anions.These studies have greatly promoted the development of the coordination chemistry and supramolecular chemistry of acylhydrazone complexes,and it is of great significance for the development of new fluorescent materials.