Preparation And Non-linear Optical Properties Of D-π-A Type Phthalocyanine Derivatives

The burgeoning advancement of laser technology has precipitated its widespread adoption across various industries.Notwithstanding the myriad conveniences lasers afford humanity,they are not without adverse consequences.High-intensity lasers,in particular,pose the risk of inflicting irreversible harm to both the human eye and delicate optical apparatuses.Consequently,optical limiting materials,underpinned by the principles of non-linear optics,are garnering increasing interest due to their rapid response time and extensive limiting range.These materials possess the capacity to attenuate the transmittance of high-intensity laser inputs,thereby safeguarding the human eye and vulnerable optical instruments from laser-induced damage.Enhancing the electron and energy transfer within the material system is instrumental in amplifying the nonlinear optical response（NLO）of organic optical limiting materials.In this regard,the development of donor-acceptor architectures has proven to be an efficacious approach for augmenting electron and energy transfer within the material system.In this dissertation,two novel D-π-A-type nonlinear optical materials,featuring distinctπ-electron bridges,were synthesized by employing phthalocyanine and fullerene as donor and acceptor moieties,respectively.A comprehensive examination of the molecular structure,photophysical properties,and the correlation between the molecular orbital energy levels and the nonlinear optical response（NLO）of tetrafullerene-substituted lanthanum metal phthalocyanine was conducted.Additionally,the relationship between the orbital energy levels and the NLO was scrutinized.The principal investigations and findings are summarized below:1)A novel D-π-A type compound,La Pc-4(C₆₀)（b）,has been synthesized,featuring lanthanum metal phthalocyanine as the donor and fullerene(C₆₀)as the acceptor.The compound was prepared via the Plato reaction,utilizing the phenyl ether bond as theπ-electron bridge.This compound amalgamates the benefits of phthalocyanine,fullerene,the rare metal heavy atom effect,and the donor-acceptor structure.Particularly noteworthy is the photoelectron/energy transfer effect（PET/ET）arising from the formation of the donor-acceptor structure within the system,which culminates in outstanding nonlinear optical properties at 532 nm and 1064 nm.The nonlinear absorption coefficient(β_eff)at 532 nm reached an impressive value of 8.4 cm/GW,surpassing the performance of single-component phthalocyanine and C₆₀.In pursuit of practical applications,the phthalocyanine derivative was incorporated into poly（methyl methacrylate）（PMMA）to fabricate phthalocyanine-polymer composite films.These films exhibited exceptional photo-limiting properties,with aβ_eff value of 2900 cm/GW.2)To further enhance the material’s nonlinear absorption coefficient,a new D-π-A type compound,La Pc-4(C₆₀)（d）,was synthesized,employing the phenylethynyl group as aπ-electron bridge.This synthesis leveraged the coplanar characteristics of the phenylethynyl group.The coplanar interaction of the phenylethynylπ-electron bridge effectively broadens the electron transport capacity,facilitating a more efficient PET/ET process.Consequently,La Pc-4(C₆₀)（d）exhibits a superior nonlinear optical response compared to La Pc-4(C₆₀)（b）,achieving aβ_eff value of 45 cm/GW at 532 nm.Moreover,the fabricated composite film(La Pc-4(C₆₀)（d）/PMMA)demonstrates an enhanced nonlinear absorption（3842 cm/GW）and a reduced limiting threshold（1.81J/cm²）.3)To gain deeper insights into and compare the electron transfer capabilities of the two compound molecules,DFT can operate the dihedral angles and the HOMO/LUMO orbitals distributions of the molecules.The incorporation of a phenylacetylene-basedπ-electron bridge serves to increase the coplanarity of the molecule,thereby enhancing the electron transfer from donor to acceptor.Consequently,the compound featuring a phenylacetylene-basedπ-electron bridge exhibits a narrower band gap,which facilitates intramolecular electron transfer and results in a more efficient PET process.Both experimental findings and theoretical calculations substantiate that the synthesized D-π-A phthalocyanine derivatives undergo PET processes,with the intramolecular electron transfer proving to be more efficient in La Pc-4(C₆₀)（d）,which contains the phenylethynyl group.This study demonstrates that the incorporation of a phenylacetylene groupπ-electron bridge can augment molecular coplanarity and enhance the efficiency of intramolecular electron transfer,consequently yielding a superior nonlinear optical response.The present work offers a novel concept and material system for the advancement of optical limiting materials with exceptional nonlinear optical properties.