Cyanide Ligated Tungsten-Copper-Sulfur Clusters:Synthesis,Structural Characterization and Third-order Nonlinear Optical Property

Author:Liu Quan

Supervisor:lang jian ping


Degree Year:2017





Interest in heterometallic Mo(W)/M/S(M = Fe,Cu)clusters is triggered by the discovery and isolation of Fe-Mo cofactor(FeMoco)in nitrogenase.With the subsequent development in its synthetic chemistry,these clusters are accordingly used as materials in nonlinear optics,catalysis,adsorption and sensing.Amongst the library of these clusters,CN-ligated clusters constitute an important subclass because of the strong binding capability of CN coupled with the flexible coordination geometry of the Cu center to provide novel cluster-based coordination oligomers and polymers.In this thesis,we explore possibilities of polydimensional W/Cu/S clusters from[Et4N][Tp*WS3(CuBr)3](P1)and[Et4N][Tp*WS3](P2)as the precursor complexes to react with CuCN as either a metal source for cluster skeletons or as a metalloligand for bridging purpose.Some key results are summarized as follows.1)In the first chapter,we summarizes CN ligated Mo(W)/Cu/S clusters,including cluster aggregates,1D,2D and 3D coordination polymers.We highlighted their synthetic methodologies and structural characteristics,and further discussed the third-order nonlinear optical properties of some examples.From these studies,we concluded that upon assembly with CN ligands,the nonlinear optical performances of these clusters have remarkably enhanced.This is probably due to the strong propensity of CN toward Cu centers that stabilizes molecular aggregates in solutions.2)In the second chapter,we explored the solvent effect on the structural outcome using the reaction of[Et4N][Tp*WS3(CuBr)3](P1)and CuCN as a model system.We isolated six chemically similar but structurally distinct coordination polymers under various experimental conditions.Including[Tp*WS3Cu3(μ3-DMF)(CN)3Cu(py)](1)from P1 and CuCN in the DMF/MeCN/py mixture at room temperature;[Tp*WS3Cu3(μ3-DMF)(CN)3Cu](2)from P1 and CuCN in the DMF/MeCN/aniline mixture at 100 ℃;[Tp*WS3Cu3(μ3-DMF)(CN)3Cu](3)from P1 and CuCN in the DMF/MeCN/aniline mixture,followed by recrystallization of the precipitate with aniline;[Tp*WS3Cu3(μ3-DMF)(CN)3Cu](4)from P1 and CuCN in the DMF/MeCN/toluene mixture under solvothermal conditions;[Tp*WS3Cu3(μ3-DMF)(CN)3Cu](5)from P1 and CuCN in the DMF/MeCN/toluene mixture at room temperature;and[Tp*WS3Cu3(μ3-DMF)(CN)3Cu(a-tolunitrile)](6)from similar reaction as that for 5 but with DMF/MeCN/a-tolunitrile mixture.Compounds 1-6 are from the same starting materials and with similar chemical components,but exhibiting different connectivity and thus structural patterns.In the presence of flexible bridging ligand bib,we also isolated a 3D compound of[Et4N]{[Tp*WS3Cu3(CN)2Br]2Cu(bib)}(7)from PI and CuCN.We investigated the NLO properties of 1-6 using four-wave mixing techniques and found that the performances of these compounds are significantly enhanced compared to that of P1.3)In the third chapter,we introduced additional pyridyl in the reaction of[Et4N][Tp*WS3](P2)and CuCN.We isolated a series of coordination polymers bearing butterfly-shaped[Tp*WS3Cu2]+ cluster cores.Including 1D polymer of[Tp*WS3Cu2CN(μ-py)]2(8)from P2 and CuCN followed by treatment of the precipitation with pyridine;1D polymer of[Tp*WS3Cu2(CN)2Cu(μ-py)2]2(9)from P2 and CuCN in pyridine solution at 80 ℃;2D polymer of[Et4N][{Tp*WS3(CuCN)2Cu}2(CN)(μ4-bipy)](10)from P2 and CuCN in the presence of bipy in CH2Cl2/MeCN/MeOH mixture at room temperature;2D polymer of[Tp*WS3Cu2(CN)(μ4-bpea)0.5]2(11)from P2 and CuCN in the presence of bpea in CH2Cl2/MeCN mixture at room temperature;3D polymer of[Tp*WS3Cu2(CN)(μ6-tpt)1/3]2(12)from P2 and CuCN in the presence of tpt in DMF/CH2Cl2 mixture at room temperature.It is surprising to note that compounds 8-12 exhibit an uncommon μ-N coordination.We investigated the NLO properties of 8-12 using Z-scan techniques and found that the performances of these compounds are significantly enhanced compared to P2.4)In the fourth chapter,we further employed reactions of P2 and CuCN in the presence of ditopic pyridyl-based ligands to construct structurally similar 1D polymers under solvothermal conditions.Reactions of P2,CuCN,NH4PF6 and pz in DMF/MeCN mixture at 100℃ afforded[Tp*WS3(CuCN)2Cu]·(pz)0.5(13).Similar compounds[Tp*WS3(CuCN)2Cu]·(4,4’-bipy)o.s(14),[Tp*WS3(CuCN)2Cu]·(bpb)0.5(15)and[Tp*WS3(CuCN)2Cu]·(bco)0.5(16)are accordingly prepared using 4,4’-bipy,bpb and bco as bridging ligands.Isoreticular compounds 13-16 represent a class of rare examples in W/Cu/S cluster chemistry.It is also notable that these compounds prepared at 100 ℃exhibit direct Cu-N association instead of μ-N type coordination found in 8-12.5)In the fifth chapter we demonstrated the synthesis of new cluster-based coordination polymers using hexamethylenetetramine(HMA)as a template.We used the alternative Cu(I)sources as surrogate for CuCN,including CuCl,CuBr,CuI,Cu(MeCN)4PF6 and obtained six compounds,viz,[Et4N]2[Tp*WS3(CuCl)3Cl](HMA)2(17),[Et4N][Tp*WS3(CuBr)3](HMA)2(18),[Tp*WS3Cu(CuCl)2(HMA)](19),[Tp*WS3Cu(CuBr)2(HMA)](20),[(Tp*WS3Cu3)2I3(HMA)2](PF6)(21)和[(Tp*WS3Cu2)(HMA)](PF6)(22),respectively.Overall,the thesis systematically explored a class of new CN ligated Mo(W)/Cu/S cluster compounds from the aspects of solvent systems,temperature,ancillary ligands and templates.Compounds 1-6 are chemically similar but structurally distinct;8-12 contains a unique μ-N type coordination mode;13-16 are rare isoreticular structures;and 17-22 are discrete molecular entities prepared with a template.We also tested the NLO properties of some of these compounds and found that the clusters ligated with CN exhibit enhanced NLO performance compared to those of their precursor complexes.