Studies On Low Temperature Solid-state Syntheses, Crystal Structures And Third-order Non-Linear Optical (NLO) Properties Of The Homo-(hetero-)nuclear Metal Clusters

Part I: Solid state reactions at low temperatureSolid state chemistry is concerned with the preparation, characterization,structure, properties and applications of solids and closely related withmaterial science and the progress of human civilization. The birth anddevelopment of solid state chemistry is closely related with mankind's needfor materials. New solid state chemistry plays an important role in thesynthesis of novel materials. Almost every new discovery in solid statechemistry had brought new breakthrough for the life of mankind , for example,electronics, optics, catalysis, energy conversion, and superconductivity etc.,which had pushed the progress of humanity's civilization greatly.Aluminosilicate zeolites are widely used in catalytic cracking, xyleneisomerization, methanol to gasoline, and detergents. A classical example isZMS-5, which did not occur in nature, was made by hydrothermal method.However, it is at the beginning of this century that solid state chemistrybecame a separate branch of physical science. New types of energy, newmaterial and information are the cornerstones of modern society. Theavailability of solid state materials with appropriate physical and chemicalproperties is the basis of new technologies. No more than one century's worksof solid state chemists have produced a large amount of sweet fruits. Suchmaterials as new high-temperature ceramic conductors, non-linear opticalsolids and thin films, supermagnetic alloys, and nano-phase catalytic materialsare promising to initiate sweeping changes in relevant technologies, includingcommunications, computing, transportation, chemical manufacturing etc. Asone of main source of new materials, solid state chemistry is acting as a moreand more important role in science and people's life today.Traditional solid state reactions usually carried out above 800oC, whichlimits the further application in industry and may cause many technical andenvironment problems. And many important metastable compounds, onlystable at lower temperatures, remain inaccessible, Chemists have developedsome methods to overcome the problems. In the flux method, the reactiontemperatures usually range from 200oC to 800oC. The temperature of thehydrothermal method is lower than that of the flux method, in general at about200oC. Another method to low the reaction temperature is "la chimie douce"(soft chemistry), which makes a single-phase solid precursor of the appropriatestoichiometry and converts it thermally to the product.Solid state reactions at low temperatures have important applications insynthesis. By this method, synthetic procedure of some compounds can besimplified and some compounds, which cannot be obtained from solution, canbe synthesized. Many interesting metastable structures can also be formed andtrapped kinetically. Several metastable compounds were prepared from thesolid state reaction at lower heating temperature. Solid state reaction at lowtemperature has attracted more and more chemists due to its high efficiency,energy saving and environmentally friendly features. Transition metals haved-orbits. Transition metal coordination compounds easily cause d-d transitionor change transfer transition. So they show dramatic colors. In this paper, aseries of transition metal complexes are synthesized by solid state reaction atlow temperature. I. Three kinds of the homo-(hetero-)nuclear metal clusters oforganic-inorganic hybrids are synthesized by solid state reaction at lowtemperature. (1) The Mo(W)/Fe/S clusters: 1. [P(Ph4)]2[Mo2O2(μ-S)2(S2)2] 2 .[Mo2O2(μ-S)2(Et2dtc)2] 3. [Fe(DMF)6]·[W2S6] 4. [Fe(DMF)6]·[Mo2S6] 5.[Fe2(Et2dtc)4] Compound 1 is consist of anion cluster [Mo2O2(μ-S)2(S2)2]2-and two[P(Ph4)]+cations. In compound, there exist two crystallographic unique Moatoms which sited in the distorted square pyramid geometry and are bridgedby μ-S atom. The linear dinuclear cluster is constructed by two three-membercycles and one four-member cycle with vertex-sharing, which lead to the greatelectron delocation. In the compound [Mo2O2(μ-S)2(Et2dtc)2] 2, there exist two crystallographicunique Mo atoms which sited in the distorted square pyramid geometry andare bridged by μ-S atom. The linear binuclear cluster is constructed by twothree-member cycles and one four-member cycle with vertex sharing, whichlead to the great electron delocation. Compound [Fe(DMF)6]·[W2S6] 3 is consist of cation [Fe(DMF)6]2+ andanion cluster [W2S6]2-, in which W atoms site in the tetrahedron geometry andare bridged by S atom to form the binuclear linear structure. Because there isno bond between the terminal sulfur atoms, only one four-member cycle isformed, and the electron delocation is not greater than that of compound 1 and2, which can be verified by the values of the third-order non-linear listed inTable I. Compound [Fe(DMF)6]·[Mo2S6] 4 is isostructural with compound 3. Compound [Fe2(Et2dtc)4] 5 is natural binuclear cluster, in with each Fe atomis coordinated by four sulfur atoms from two (Et2dtc)-ligands, and the trianglebipyramid is completed by the fifth sulfur atom from the third (Et2dtc)-ligandwhich chelates to the other iron atom. Just due to the weak coordinationreaction, the binuclear cluster with a edge-sharing (S3-S3A) doubletriangle-bipyramid is construed. (2) The Mo(W)/Cu(Ag) clusters: 6. [MoOICu3S3(2, 2.-biby)2] 7. [WM2S4(PPh3)3]·DMF (M2 = 1.25Ag + 0.75Cu) 8. {[(t-Bu)4N]2[Ag6I8]}n 9. [Cu(Him)4(CH3CH2OSO3)2] The skeleton of compound 6 [MoOICu3S3(2, 2.-biby)2] is an open-cubane,in which Mo, Cu1 and Cu2 atoms all site in the distorted tetrahedrongeometries, While Cu3 sites in triangle. The cluster units [MoOICu3S3(2,2.-biby)2] are linked to each other to form 3-D supramolecular network by thehydrogen-bond and π-πinteractions. Compound [WM2S4(PPh3)3]·DMF(M2 = 1.25Ag + 0.75Cu) 7 is constructedby a trinuclear cluster with PPh3 auxiliary ligand and the solvate moleculeDMF. Two moieties [M(PPh3)]+ and [M(PPh3)2]+are linked by [WS4 ] through 2-four sulfur atoms, and the W center sites in the tetrahedron geometry. Thelinear type cluster is constructed by two four-member cycles withvertex-sharing, Which lead to great election delocation. Compound {[(t-Bu)4N]2[Ag6I8]}n 8 is consist of cation [(t-Bu)4N]+ andanion cluster [Ag6I8]2-. The hexnuclear Ag-I cluster is constructed by twodistorted cubanes [Ag4I4] with sharing-plane. These plane-sharing doublecubanes [Ag6I6] are connected by the other two I atoms to form the 1-Dlimitless chain, which lead to great electron delocation. In compound [Cu(Him)4(CH3CH2OSO3)2] 9, Cu atom locates at thecrystallographic center and sites in octahedron geometry center with N1, N3,N1a, N3a and the anis O1, O1a. It is two kinds intermolecular hydrogen bondinteractions link the mononuclear compounds to 2-D supramolecular network. (3) The Mo(W)/O compounds: 10. [WO2(C9H6NO)2] 11. [(t-Bu)4N]2[Mo6O19] 12. [(t-Bu)4N]2[W6O19] In the neutral compound [WO2(8-hq)2] 10, W center sites in the distortedoctahedron geometry. The mononuclear coordination compound is linked to3-D network by three kinds intermolecular hydrogen-bonds. Compound [(t-Bu)4N]2[Mo6O19] 11 is consist of [(t-Bu)4N]+ cation and[Mo6O19]2-anion cluster. There are crystallographic unique three kinds ofoxygen atoms and six Mo atoms. Each Mo atom is coordinated to six oxygenatoms and sites in the distorted octahedron geometry. For compound [(t-Bu)4N]2[W6O19] 12, there are two crystallographic uniquemolecules in the asymmetry unit. Compound 12 is isostructural withcompound 11. II. Transition metal complexes are synthesized by solid state reaction andcharacterized by UV-visible, IR, XPS, ESR spectra. It is found that solid statereaction at lower temperature is better than liquid phase reaction in yield,operation convenience.Part II: The third-order Non-linear optical properties The design and synthesis of new molecules with large macroscopicnonlinear optical properties represent an active research field in modernchemistry, physics and material science. Nonlinear optics is one of a fewresearch frontiers where tremendous interest arises not only from the requestfor understanding of a new physical phenomenon but also from the potentialtechnological applications. The chemistry of transition metal-sulfur/nitrogenclusters has attracted much interest recently owing to their relevance topotential application in nonlinear optical materials. Mo(W)-Cu(Ag)-S(N)clusters have been found to have interesting structures and good nonlinearoptical (NLO) properties. We found that there are four important factors on thenonlinear optical effects of transition metal clusters: (1) skeleton structureeffect, self focusing effects and self defocusing effects vary with the corestructures; (2) heavy atom effects, cluster skeletons with heavy atoms exhibitbetter NLO effects than those with lighter atoms; (3) polymerization effects,polymerization could result in an enhancement of optical limiting effects; (4)ligands effects, peripheral ligands have a considerable impact on NLO effects.Polymeric clusters are of special interest mainly due to their properties: mostpolymeric species possess robust thermostability and exhibit greatphotostablity toward the photodegradation reflection process associated withterminal ligand substitution by solvents, especially toward the light-inducedfragmentation caused by electron transition between the skeleton bonding andantibonding orbitals. Both of above features represent a unique opportunity forprobing correlation between the structure and properties. This dissertationbroaden the research scope of clusters and nonlinear optical materials topresent several research directions as follows: 1. Since the metal cluster compounds by low temperature solid-statesyntheses have good second and third nonlinear optical properties, the authorintroduce the ligands containing N, S, P into the synthesis ofMo(W)/Fe/Cu(Ag)/S clusters, and synthesized six clusters. They are linearclusters [P(Ph4)]2[Mo2O2(μ-S)2(S2)2] 1, [Mo2O2(μ-S)2(Et2dtc)2] 2,[Fe(DMF)6]·[W2S6] 3, [Fe(DMF)6]·[Mo2S6] 4, [Fe2(Et2dtc)4] 5, and[WM2S4(PPh3)3]·DMF (M2 = 1.25Ag + 0.75Cu) 7. Compound [WM2S4(PPh3)3]·DMF(M2 = 1.25Ag + 0.75Cu) 7 is isostructuralwith compound [WS4Cu2(PPh3)4]. But the values of NLO parameters is largerthan that of compound [WS4Cu2(PPh3)4]( α2 = 3.7×10-11 m/w, n2 = 2.1×10-18m2/w) because the Ag atom in compound 7 is heavy than Cu atom, which isverified by the heavy atom effects. Cluster 7 exhibits self-defocusing propertyand the reverse saturation absorption Clusters 1-5 have the nicer third-order NLO performance, and display thereverse saturation absorption (α2 > 0) and self-defocusing properties (n2 < 0).We can attribute the nicer NLO properties of the compounds 1-5 to the largedelocaltion electron cloud due to the vertex-sharing three/four-member cyclesand the electron-donor S atoms, which can be explained by the skeletonstructure and ligands effects. 2. Based on structure effects and molecule design, one mononuclear clustersand an oligomeric cluster with good NLO effects were synthesized. In thestructure of nest cluster [MoOICu3S3(2, 2.-bipy)2] 6 there exists a smallerCu-Mo-Cu angle than that of other similar cluster which makes the wholemolecule exhibit a distinct angle shape structure. A polynuclear silver (I)complex {[(t-Bu)4N]2[Ag6I8]}n 8 with iodo-bridging ligands has been prepared;the centrosymmetric cluster anion can be described as two [Ag4I4] distortedcubane units sharing one [Ag2I2] plane. The special structure of the twoclusters lead to the large π-electron system and great electron delocation, Sothe two clusters both show strong third order non-linear absorption andrefraction. White the NLO property of 8 is better than that of 6, which can beexplained by the polymerization effects. 3. Compound [Cu(Him)4(CH3CH2OSO3)2] 9 and [WO2(C9H6NO)2] 10 areboth mononuclear structure and performance good reverse saturationabsorption absorption and self-defocusing refraction. While the NLO propertyof 9 is better than that of 10, probably because the supramolecular structure of9 contain more hydrogen-bond and π-πinteractions. 4. The structures of compounds 11 and 12 are similar, the NLO property of12 is better as suspected because of the heavy atom effect.