Research On The Cluster Or Cage Structure Based On Redox-active Ligands

Redox isomerism,also called valence isomerism,is the phenomenon of a reversible charge transfer between a metal and a ligand.The charge transfer between the metal and the ligand is expected to realize the change of structure.There are many conditions for charge transfer,for example,external stimuli such as temperature,pressure and the addition of oxidants.There are two key points involved in this system:one is the metal center with redox-activity(such as Co,Fe,Mn in transition metals and Ce,Sm,Pr in rare earth metals);The other is a redox-active ligand(e.g.,bis(bidentate)oxo-or thio-benzoquinoid bridging ligands,tetrathiofvalene derivative bridged ligand,and dioxime ligand).Clusters and cages with different structures can be obtained by selecting suitable redox-active ligands.The chelating/bridging ligand H₂acnd is utilized,because it comprises four oximate-based donor sites and the bulky acenaphthene functionality which is beneficial for the formation of polynuclear clusters.As our continuous interest on 3d-4f chemistry,we aim to explore new 3d-4f supertetrahedral clusters.Mixed metal Mn ^III-Ce ^IVclusters attract our attention because they have been rationalized on the fact that Mn ^IIIion is a hard acid forming polynuclears with the hard O^2–ligands that in turn favor incorporation of the hard Ce ^IVion thus leading to polynuclear Mn ^III-Ce ^IVclusters.Herein,we report a molecular supertetrahedral T2 cluster which comprises six different kinds of ligands.In the field of supermolecule,obtaining supramolecular cage structures with high stability has always been one of the challenging topics.Many supramolecular structures often collapse due to the removal of solvent molecules,which makes it impossible to further study their properties.supramolecular system is prepared by the non-covalent interactions,which mainly include hydrogen-boding and so on.Hydrogen bonding is more common form in supramolecular chemistry.The bis(bidentate)oxo-benzoquinoid bridging ligands(such as chloranilic acid(Cl₂An),bromanilic acid(Br₂An),etc.)containing strong electronegative atoms exhibit unique and excellent properties in the process of assembling into supramolecular cage structures.In this paper,by selecting the smaller steric-hinerance effect N,N,N',N'-Tetrakis-(2-pyridylmethyl)ethylenediamine as the ancillary ligand,the bis(bidentate)oxo-or thio-benzoquinoid bridging ligands chloranilic acid(Cl₂An),bromanilic acid(Br₂An)containing strong electronegative atoms as the tetradentate bridging ligangs,metal salt containing strong electronegative atoms as the counter ion,combining with reasonable design to form the necessary building blocks,We have successfully obtained two new supramolecular cages with different structures and properties.1)by selecting the smaller steric-hinerance effect N,N,N',N'-Tetrakis-(2-pyridyl methyl)ethylenediamine as the ancillary ligand,the bis(bidentate)oxo-benzoquinoid bridging ligands chloranilic acid(Cl₂An)or bromanilic acid(Br₂An)containing strong electronegative atoms as the tetradentate bridging ligangs,solids Cerium(?)perchlorate hexahydrate containing strong electronegative atoms as the metal salt,combining with rational design and control of reaction conditions,We have successfully obtained a tetranucleate square building block bridged by chloranic acid.We make a determination of the structure.In addition,the magnetic data was measured and studied,and the magnetic data related to them were fitted theoretically.Combined with their crystal structure,the magnetic data of them were reasonably explained.It was found that the complex had weak antiferromagnetic interaction,and there could be a case of charge transfer.Finally,due to its relatively stable cavity structure,we made a comprehensive analysis of its gas adsorption performance and separation performance.Our experiment demonstrated that the supramolecular cage is able to reversibly uptake dialkyl and trialkyl gases.It also can be observed from the isotherm plots that the supramolecular cage has the stronger adsorption capacity to dialkyl and trialkyl gases.This information will urge us to compare adsorbent efficacy for removing dialkyl and trialkyl gases and separating dialkyl and trialkyl gases from other gases and other applications.Furthermore,it exhibits better separation properties for mixed gas systems of C₃H₈/CH₄(15/85,v/v),C₂H₆/CH₄(15/85,v/v),CH₄/CO₂(50/50,v/v),C₂H₂/CO₂(50/50,v/v)and N₂/CO₂(85/15,v/v)mixture under ambient conditions(298K,1bar).Obviously,the separation capacity of the supramolecular cage1 for C₃H₈over CH₄is best.2)by selecting the smaller steric-hinerance effect N,N,N',N'-Tetrakis-(2-pyridyl methyl)ethylenediamine as the ancillary ligand,the bis(bidentate)oxo-benzoquinoid bridging ligands bromanilic acid(Br₂An)containing strong electronegative atoms as the tetradentate bridging ligangs,solids sulfuric acid ammonium cerium salt dihydrate as the metal salt,combining with rational design and control of reaction conditions,We have successfully obtained a dinucleate Z type building block bridged by bromanilic acid.We make a determination of the structure.In addition,the magnetic data was measured and studied,and the magnetic data related to them were fitted theoretically.Combined with their crystal structure,the magnetic data of them were reasonably explained.It was found that the complex had weak antiferromagnetic interaction,and there could be a case of charge transfer.In addition,the stability analysis showed that the structure of the supramolecular cage compound collapsed completely after desolvation treatment,so it was impossible to study its host and guest system.3)by selecting the smaller steric-hinerance effect N,N,N',N'-Tetrakis-(2-pyridyl methyl)ethylenediamine as the ancillary ligand,the bis(bidentate)oxo-benzoquinoid bridging ligands bromanilic acid(Br₂An)containing strong electronegative atoms as the tetradentate bridging ligangs,solids Cerium Nitrate Hexahydrate salt or Ceric Ammonium Nitrate as the metal salt,combining with rational design and control of reaction conditions,We have successfully obtained a supramolecular octahedral cages of self-assembly through coordination interactions.We make a determination of the structure.In addition,the magnetic data was measured and studied,and the magnetic data related to them were fitted theoretically.Combined with their crystal structure,the magnetic data of them were reasonably explained.It was found that the complex had weak antiferromagnetic interaction,and there could be a case of charge transfer.4)by using acenaphthenequinone dioxime(acnd H₂)as chelating/bridging ligand and using manganese(II)chloride tetrahydrate and cerium(III)acetylacetonate hydrate mixed metal as 3d/4f system,combining with rational design and control of reaction conditions,We have successfully obtained a molecular supertetrahedral T2 cluster which comprises six different kinds of ligands.We make a determination of the structure.In addition,the magnetic data was measured and studied,and the magnetic data related to them were fitted theoretically.Combined with their crystal structure,the magnetic data of them were reasonably explained.It was found that the complex had weak antiferromagnetic interaction.Since the crystal data of the molecular supertetrahedral T2 cluster is monoclinic chiral space group P2₁,its chiral structure makes us study its second-order nonlinear optical properties.Its SHG efficiency was about 0.84%of commercial KDP.The weak SHG effect is attributed to the helical arrangement of the discrete T2supertetrahedral chiral structure,because chirality belongs to one of the non-centrosymmetric(NCS)crystal structures.The above results indicate that new molecular supertetrahedral T2 clusters with different structures can be synthesized by properly selecting redox active ligands and combining with 3d/4f mixed metal system.The necessary building units can be formed by selecting auxiliary ligands with small steric resistance,redox active bridging ligands and the counter ion with strong electronegative atoms,and combining with reasonable design to form new supramolecular cages with different structures and properties.