Preparation And Nonlinear Optical Properties Of Corroles And Corrole Functionalized GO Nanohybrids

Due to the merits such as the structure with flexible tailor and adjustable performance,etc.,organic nonlinear optical（NLO）materials have attracted widespread attention since the last decade.In order to fully expand their applications in ultrafast photonics,optical power limiting,optical communication and data storage devices,design and synthesis of new organic compounds with excellent NLO properties has been of great interest for researchers.Corroles,as a new type of tetrapyrrole compounds,contain 18πelectrons.There are three NH protons in the inner core,which can coordinate with many kinds of metels.At the same time,all the H atoms at theβand meso positions can be replaced by different kinds of substituents.Therefore,subtle variation in their physical properties can be tuned by the placement and properties of the substituents or the central metals.Compared to porphyrins,corroles lack one meso carbon atom.Accordingly,corroles have a smaller four-nitrogen cavity and lower symmetry,which make corroles can be an excellent NLO materials.A series of novel corroles and corrole modified graphene oxide（GO）nanohybrids were designed and prepared.The nonlinear optical behavior was investigated using Z-scan techniques.The main studies are as follows:1.Synthesis,characterization and third order nonlinear optical properties of trans-A₂B-type cobalt corrolesMany kinds of organic molecules with a large polarizableπ-electron conjugated system,such as perylene diimides,porphyrins,phthalocyanines,are known as NLO materials.Corroles,as porphyrin analogues,are akin to porphyrins with 18π-electron tetrapyrrolic macrocycles with one less meso carbon atom but one additional inner NH proton.The special feature and excellent properties have made corrole chemistry flourish prominently in recent years and led to their applications in the fields of catalysis,sensors,solar cells,and medicinal chemistry.However,studies on the NLO applications are rare.A series of trans-A₂B cobalt corroles,represented as[Cor（p-RPh）₂（p-NO₂Ph）]Co（PPh₃）（1-5）,where Cor is trianion of corrole,R is a CN,F,CH₃,C（CH₃）₃or Ph CH₂O on the para-position of the 5-and 15-meso-phenyl rings of the macrocycle,and NO₂ is on the para-position of the 10-meso-phenyl rings of the macrocycle,were designed and synthesized.Structural elucidation of the investigated cobalt corroles was carried out with common spectroscopic methods such as ¹H-NMR,FT-IR,UV-vis and MALDI-TOF-MS.Each cobalt corrole undergoes two reversible one-electron oxidations and three reductions with E_1/2 values being linearly related to the sum of the Hammett substituent constants（Σσ）.The third-order nonlinear optical（NLO）properties of these corroles were evaluated in DMF by the Z-scan technique characterized as showing nonlinear reverse saturation absorption and self-defocusing behavior.The values of large nonlinear refractive index（n₂）and the two-photon absorption coefficients（β）were in the range of（-）1.25-1.50×10^-13 cm²/W and（1.05-1.45）×10^-9cm/W,respectively,making the current cobalt corroles a promising possibility for optical limiting applications.2.Preparation and nonlinear optical properties of corrole functionalized GO nanohybridsOrganic-inorganic hybrids has opened a new interest in nonlinear optical materials.Due to its extendedπ-conjugate system and excellent NLO performances,graphene oxide（GO）is the most popular inorganic material.Many researches during the past several years has focused on the porphyrin/phthalocyanine functionalized graphene nanohybrids for optical limiting applications.Three new hydroxyl-substituted trans-A₂B corroles PC,NAPC and PYPC were designed and synthesized here.And accordingly,the corrole functionalized graphene oxide（GO）nanohybrids were prepared by the in situ synthesis of corroles on the surface of GO.The obtained nanohybrids are represented as PC-GO,NAPC-GO and PYPC-GO,respectively.The covalent functionalization between corrole and GO is fully confirmed by various spectroscopic techniques.The nonlinear optical behavior of GO,free base corroles and their corresponding nanohybrids in DMSO was investigated using open aperture Z-scan techniques.A shift from saturable absorption（SA）for GO to reverse saturable absorption（RSA）for nanohybrids was observed at low input pump intensity.