Synthesis And Properties Of Transition Metal Clusters Based On Pyrazol Derivative Ligands

The flourish of research into nanosized polynuclear metal clusters has been motivated by their aesthetically pleasing structures and promising physicochemical properties and applications,such as molecular magnets,catalysis and molecular electronics.A lot of work has been done over the past years in exploring the different synthetic strategies for the construction of polynuclear metal nanoclusters.Among which,the elaborate design or selection of the multidentate chelating ligands with various configurations and coordination sites to capture multiple metal ions have proven to be one of the most powerful approaches.In this thesis,we designed and synthesized two pyrazol alcohol ligands:1-(hydroxymethyl)-3,5-dimethylpyrazol(HL)and 1,2-bis-(3,5-dimethylpyrazol-1-yl)-ethane-1,2-diol(H2bdped),and synthesized ten different transition metal compounds by using these two ligands.The structures of these compounds were measured by X-ray single crystal diffractometer and the properties were characterized by some basic characterization techniques such as Infrared spectra,optical UV-Vis,X-ray powder diffraction and thermogravimetry.Electrospray Ionization Mass Spectrometry was also employed in order to explore the assembly mechanism of the clusters.The main research work of this paper is as follows:Chapter one:Preface.The basic concepts of transition metal clusters were introduced and the synthesis methods,influencing factors and basic properties of metal clusters are emphasized.Chapter two:Self-Organization into Preferred Sites by Mg?,Mnu,and Mn? in Brucite-Structured M19 Cluster.We have successfully synthesized Mn19 clusters by using HL ligands.In this chapter,the doping of Mg? in Mn19 was successfully realized by controlling the adding time of Mg(NO3)2 in Mn19 system.Finally,the compound Mn13Mg6,[Mn13Mg6(L)18(OH)12(N3)6]·(C104)6·12CH3CN(1),was obtained and the basic characterizations were carried out.Its solution behavior was studied by Electrospray Ionization Mass Spectrometry(ESI-MS).The mechanism of the reaction was investigated by Mass Spectrometry through monitoring of the parent liquor before and after adding Mg(NO3)2.Chapter three:Novel copper(?)and nickel(?)clusters based on bi(pyrazolyl-alcohol)ligand:synthesis and properties.The novel Cu9 compound,[Cu9(bdped)4(N3)4(ba)3(OAc)3]·EtOH·H2O(2)and Ni6 compound,[Ni6(bdped)2(OAc)8(H2O)4]·6EtOH(3)were synthesized at room temperature by the reaction of H2bdped ligands with Cu2(OAc)4·2H2O and Ni(OAc)2·4H2O,respectively.Basic characterizations of the two compounds 2 and 3 were measured.We also studied their solution behavior and magnetic properties.The results show that some metals keep the structural skeleton stable.Chapter four:Self-assembly of a nonanuclear Ni? cluster via atmospheric CO2 fixation:synthesis and properties.A new topological compound Ni9,[Ni9(OH)6(CO3)2(ba)8(hdmpz)6(DMF)2]·EtOH-2DMF(4)was synthesized by using 3,5-dimethylpyrazol ligand(Hdmpz)in base environment.Interestingly,CO2 derived from atmosphere was absorbed in solution to form CO32-template which further connected nine nickel atoms in the cluster center to form a "drum" structure core.The solution behavior and gas phase behavior of compound 4 were studied by Electrospray Ionization Mass Spectrometry in detail.The results of Mass Spectrometry showed that compound 4 maintained the integrity of metal skeleton structure in the solution.However,in the gas phase,when the collision energy was small,the loss of neutral ligands is the only channel for the fragment of the compound,and the fragmentation becomes more complicated with the increase of collision energy up to 20 eV.Chapter five:Copper(?)-Assisted Ligand Fragmentation Leading to Three Families of Metallacrown.We used H2bdped ligands to react with different copper salts in base condition.Interestingly,nine different multidentate ligands were generated by in-situ reaction of H2bdped ligands in different alcohol-containing solutions.Cu6:Cu6(?8-et)(?2-dp)4(?4-dpmed)2(dmf)2·3.5MeOH(5),Cu6(?8-et)(?2-dp)4(?4-dpet)2(dmf)2(H2O)·3H2O(6),Cu8:Cu8(?2-OAc)6(?6-bdped)2(?6-met)2·4MeOH(7),Cu8(?2-OAc)6(?6-bdped)2(?6-eet)2(EtOH)2·6EtOH(8),Cu8(?2-OAc)6(?6-bdped)2(?6-pet)2(iPrOH)2·3iPrOH?2CH2C12(9),Cu16:Cu16(?3-OH)4(?8-et)2(?2-dp)16(?4-ox)2(EtOH)2·1 OEtOH(10),were successfully synthesized with above nine ligand.The solution behavior of compounds 6,8,10 were studied by Mass Spectrometry.The results show that all of the compounds maintain the stability in the solution.