| Part1The laser has been applied to all aspects of national defense science and technology and our daily lives, which brings us great convenience, as a consequence, nonlinear optical (NLO) materials rather than traditional linear materials are the object of a growing interest because of their potential applications as photonic devices, optical limiting, optical data storage, light frequency converter and so on. In this context, materials based on third-order nonlinear optical effects are the most promising. Among the various classes of NLO materials, porphyrins are generally more attractive because of their many distinguish properties especially highly delocalized aromatic π-electron system and therefore, numbers of different strategies are adopted to improve and optimize NLO properties for porphyrin-based materials. However, the exhibiting NLO responses are rather confined because many limitations are associated with such kind of strategies. Therefore, it is still need to find a simple strategy that can give rise materials with better third order NLO responses. In this regards, we proposed a new strategy by integrating polyoxometalates into porphyrin moieties via covalent bond which is expected to be a new approach to tune and enhance the nonlinear optical responses of porphyrins.In this part, the following main achievements are obtained: 1) Seven new porphyrin-polyoxometalates based hybrid compounds are synthesized and structurally characterized by electro-and spectro-chemical measurements. The nonlinear optical responses of all the compounds were studied by well known Z-scan technique. The innovative achievements of the paper include:a) First we designed the new approach to tune and enhance the nonlinear optical responses of porphyrins. The effectiveness and efficiency of this proposed new approach has been examined and witnessed by studying two new hybrid compounds, namely, HNC(CH2O)3P2V3W15O59]·2(C4H9NO)(1) and HNC(CH2O)3P2V3WI5O59]·3(C4H9NO)(2)(TBA=tetrabutylamunium), which are synthesized by connecting porphyrins and Dawson type polyoxometalate via short tether through covalent bond and thoroughly characterized by elemental analyses,1H NMR, ESI-MS, FT-IR, and UV-vis., fluorescence emission spectra, TG-DTA and spectro-electrochemical studies. Investigations by the well established Z-scan technique reveal that remarkable enhancement in reverse saturation absorption is achieved in1and2which is comparatively ca. one order greater than their individual reactants.b) Second, in order to investigate the structure-property relationship of porphyrin-POMs hybrid systems which are expected to be good candidates as NLO materials, a family of new covalently bonded hybrid compounds, namely,[N(C4H9)4]3[MnMo6O18{C5H9O3}2]-2H2O (1),[N(C4H9)413[C52H34N502(OCH2)3CNH2｝MnMo60:8(C5H903)].CH3C(O) N(CH3)2(2),[N(C4H9)4]3[(C49H36O4N5)MnMo6O18(C5H9O3)]-CH3C(O)N (CH3)2(3),[N(C4H9)4]3[MnMo6O)8{C52H34N5O2(OCH2)3CNH2}2]-2H2O旵H2C12(4) and [N(C4H9)4]3[MnMo6Oi8{C49H36O4N5}2](5) have been synthesized and characterized thoroughly. The third order nonlinear optical (NLO) responses of all the compounds are studied by well establish Z-scan technique. Investigations of nonlinear optical properties (NLO) reveal that the compounds2-5show remarkable enhancement in nonlinear reverse saturable absorption and self-defocusing effect under open-and closed-aperture configuration respectively while compound1did not show any response. The results further show that the closer is better and two is superior to one i.e., directly POM linked porphyrin is better than that porphyrin which is linked via linker as well as two porphyrins directly connected to POM show more enhancement than single connected porphyrin. Optical-limiting (OL) thresholds are obtained being ca.,0.987,0.831,0.697,0.51J/cm2for compounds2-5respectively, implying their high potential as OL materials.Part2The design of new inorganic-organic hybrid compounds, based on sandwich type POMs as building blocks incorporating with transitional metals molybdophosphate, are of growing interest because of their fascinating structural frameworks as well as their potential applications such as conductivity, catalysis and in material chemistry. In this part, the following main achievements are obtained:One new compound based on the sandwich type POM as building block is synthesized hydrothermally and its structure is characterized by using different techniques i.e., elemental analyses, UV-vis., infrared spectroscopy and single crystal XRD as well as their catalytic activity is also measured. The innovative achievements of the paper include: The structural comparison of the new compound,[(bpp)3H6]Fem2FeH2MoV24HPO4)4(PO4)4(H2PO4)8O48(H2O)4(OH),2]·2H2O (1)(bpp is denoted as1,3-di(4-pyridyl)propane) and those of two previously reported compounds, viz.,[FeⅡ(bpy)3]3[FeⅡ2FeII12MoV24(HPO4)4(H2PO4)8(OH)12(PO4)4O48(H2O)4]-12H2O (2) and [FeⅡ(bpy)3]2FeFeⅢMov12(H2PO4)2(H1+XPO4)(H2-XPO4)(PO4)2(HPO4)2O24H2O)2(OH)6]·9H2O(x=0and1)(3)(bpy is denoted as2,2’-bipyridine), which exhibit one-dimensional mixed-valence iron molybdophosphate anionic chains constructed by alternating units of FeⅧ ions and magic [FeⅡ(Mo6P4O31)2] units, revealed that the same atomic ratios of Fe, Mo, O, and P within the polymeric anionic chains remain same for all three compounds, while the polymeric anionic chains of different compounds bear different numbers of negative charges, therefore different numbers of counter cations per {FeⅢ2[FeⅡ2(P16MoⅤ24)]} unit in the compounds. It is disclosed that not only the spatial assembling of counter cations and polymeric inorganic chains in the three compounds are quite different, but also the O-FeⅢ-O bond angles and FeⅢ-0bond lengths of three different inorganic chains are slightly different. What important is that such small changes in the bond angles and lengths in the assemblage of FeⅢ-0bonds lead to the considerable fluctuations of inorganic chains in their structural conformation within three compounds, reflecting an interesting "flexibility" in pure inorganic one dimensional mixed-valence iron molybdophosphate chains. |
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