Fabrication Of Several Polyoxometalates-Porphyrins Hybrid And Their Third-order Nonlinear Optical Properties

Since the porphyrin ring has 18 conjugated electrons and the porphyrin ring is easily modified,the porphyrin exhibits excellent nonlinear optical properties and fast response.And polyoxometalates(POMs)can accept electrons reversibly without changing their structures significantly,so POMs have huge application prospect in the nonlinear optics field.On the other hand,hydrotalcite contains a large amount of charge and has the ion exchange capacity which attracted extensive attention.In this paper,porphyrins and polyoxometalates were covalently linked to obtain their hybrid polymers,and the third-order nonlinear optical response of the composites was improved;In addition,porphyrins and polyoxometalates are intercalated into the hydrotalcite layers by ion exchange to promote the interaction between them,thereby further enhancing the third-order nonlinear optical response of the composites.Under the excitation of nanosecond laser,the third-order nonlinear optical properties of porphyrin-polyacid hybrid polymer and intercalation complex were studied by Z-scan,the main achievements of this paper are as follows:1.Two hybrid polymers {[N(C4H9)4]2H[Mn ? Mo ?6O18(OCH2)3CNHCOC44H30N4CNHCO(OCH2)3]·6H2O}n(HP1)and{[N(C4H9)4]2H[Mn ? Mo ? 6O18(OCH2)3CNHCOC42H28N6CNHCO(OCH2)3]·6H2O}n(HP2)were fabricated by connecting 5,10-tris(4-phenyl)15,20-(4-carboxymethylphenyl)porphyrin(C54H48N6O8 BPP)and 5,10-tris(4-pyridyl)15,20-(4-carboxymethylphenyl)porphyrin(C52H46N8O8 BBPP)which have good third-order nonlinear optical properties with Anderson type polyoxometalates[N(C4H9)4]3[MnMo6O18{(OCH2)3CNH2}2](Abbreviated as MnMo6O18)through tris(hydroxymethyl)aminomethane.Their compositions and structures were characterized by FT-IR,UV-vis,1HNMR,elemental analysis,ESI-MS and cyclic voltammetry.And the effects of polyoxometalates in polymers on the third-order nonlinear optical properties of porphyrin was studied.The nonlinear optical properties of the two hybrid polymers were further compared with its individual repeating unit hybrid[N(C4H9)4]3{C44H29N4CONHC(CH20)3Mn ? Mo ? 6018(OCH2)3CCH3 ·CH3C(O)N(CH3)2}(H3)and two other compounds synthesis by Hafiz Muhammad Asif of our group[N(C4H9)4]3[C98H72N10O26Mn?Mo?6]·5H2O(H4)and[N(C4H9)4]3[C98H66N16O26Mn? Mo ? 6]4H20(H5).They exhibited a saturable absorbtion property and self-defocus behavior by Z-scan which was performed at 532 nm and 6 ns.Third-order nonlinear polarization ?(3)value of the polymers reach 2.56 × 10-10(esu)(Hybrid polymer 1)and 2.57 × 10-10(esu)(Hybrid polymer 2)which are larger than repeating unit H3(1.55 × 10-10(esu))and compounds H4,H5(1.87 × 10-10(esu)and 2.20 × 10-10(esu)respectively).The third order nonlinear polarizability ?(3)of the hybrid polymers is proportional to the LUMO energy level difference between the ligand porphyrin and POMs and is inversely proportional to the HOMO-LUMO energy gap Eg of the polymer itself.This may be due to the formation of an electron donor-acceptor system between porphyrin and POMs,which increases the range of electron mobility and the chain structure of the polymer is more favorable for electron and energy transfer between porphyrin and POMs.2.Single intercalation complexes[(P5W30)x-(TCPP)y/LDH](x = 0 Abbreviated as 1;y = 0 Abbreviated as 17)(x/y is the composition ratio of P5W30 and TCPP in the product)and the intercalated layer complex[(PSW30)x-(TCPP)y/LDH]2-16 were prepared by exfoliation-retacking with meso-tetrakis(p-carboxyphenyl)porphyrin,Preyssler-type polyoxometalate(POM)and MgAl layered double hydroxide(LDH).By adjusting the ratio of POMs and porphyrins in the reaction solution to obtain different cointercalation compounds.The compositions and structures were characterized by FT-IR,XRD,ICP-AES and elemental analysis.The third-order nonlinear optical properties of P5W30 and TCPP mixed solutions and different proportions[(P5W30)x-(TCPP)y/LDH 1-17]were studied by Z-scan method.These cointercalation compounds had reverse saturated absorption property and self-defocus behavior.When the concentration of porphyrin was the same in the suspension of cointercalation compounds,the nonlinear effect of suspensions increased with the ratio of POM and porphyrin in the interlayer increased.The donor-acceptor interaction of POM and porphyrin was considered to enhance the nonlinear effect of porphyrin in the interlays.Until the added ratio of the amount of mole of P5W30 and TCPP reaches x/y = 25.34/35 which is intercalation complex 12 reaches the strongest and then begins to decrease gradually.