Structures, Spectrum Properties And OFET Performance Of Phthalocyanine Complexes Based On Density Functional Theory Calculations

Phthalocyanines and porphyrins are two important classes of pigments which have found their applications in various disciplines.The number and dispositions of the substitutions affect the electronic absorption,Infra-red(IR),and Raman spectra of the phthalocyanine complexes.Study on the relationship of their structures and properties is of great importance on designing new phthalocyanines with novel properties and material performances.Organic field effect transistors(OFETs) have attracted increasing research interests due to their great potential applications in the field of flexible displays,integrated circuits,and low-cost electronic devices.In recent years,many organic semiconductors with good OFET performance have been developed and significant progress in OFET fabricating techniques has been made.Phthalocyanines have been among the most intensively studied small molecules with excellent semiconductivit.A series of phthalocyanine compounds have been fabricated into the OFET devices and their OFET performance has been studied.In the past two decades,theoretical and computational efforts have been paid towards understanding and designing novel molecular semiconducting materials with good OFET performance.Our research work has been focused on the following respects:1.Structures and properties ofβ-octasubstituted phthalocyaninato-leafl complexes Density Functional Theory(DFT) and time-dependent Density Functional Theory(TD-DFT) calculations were carried out to comparatively describe the molecular structures,atomic charges,molecular orbital energy gaps,UV-vis spectra,infrared(IR) and Raman spectra of Pb[Pc(R)₈](R=F,Cl,Br,H,-CH₃,-C₂H₅,-C₃H₇).Both the calculated structure and infrared spectrum of PbPc are in good correspondence with the experimental results.It has also been found that substitution of electron-withdrawing halogen groups and electron-donating alkyl groups at the peripheral positions of phthalocyanine ring adds obvious and different effect to the structures and properties of phthalocyaninato lead compounds.The change rules of the parameters studied have no linear relationship with the Hammett constants of the substitutents due to the complexity of phthalocyanine macrocycle.2.Structures and properties of tetrakis(thiadiazole) porphyrazine based on density functional theory calculations Phthalocyanine compounds have received extensive attention in the past century because of their peculiar and unconventional chemical and physical properties such as chemical inertness,semi-conductivity,photoconductivity,and catalytic activity.Various chemical modifications have been carried out mainly on the benzene ring in phthalocyanine to tune the physical properties.Recently,a new series of porphyrazine compounds that bear peripheral annulated 1,2,5-thiadiazole(or 1,2,5-selenodiazole) have been reported.These new types of porphyrazine systems can be identified as phthalocyanine analogues considering that the external thiadiazole and selenodiazole skeletons are both isoelectronic in terms ofÏ€electrons with the H₂Pc skeleton.In addition to N atoms,the presence of soft atoms such as S or Se in the peripheral heterocyclic rings is expected to tune the electronic configuration of the macrocycle and corresponding physic-chemical properties.As a result,this series of new phthalocyanine analogues are promising new materials with potential applications in different fields.However,there seems no theoretical study on this series of compounds.The molecular structures,atomic charges,molecular orbital,UV-vis,and infrared(IR) spectra of TTDPzH₂,TSeDPzH₂,and TTDPzCu were studied by DFT calculations.The calculated structural data and the simulated UV-vis and IR spectra of TTDPzH₂ are in good agreement with the X-ray crystallography structures and the experimental absorption spectra.It has been found that the soft atoms such as S or Se together with the nitrogen atoms in the peripheral heterocyclic rings have more effects on the charge distribution of C_βatoms than the other atoms.Media effects can only have small influence on the charge distribution of TTDPzH₂ and TTDPzCu.The natures of the main transitions in electronic absorption spectra of the three compounds have been assigned.3.Structure and spectroscopic properties of phthalocyaninato zinc(â…¡) complexes fused with different number of 15-crown-5 moietiesWe have designed,prepared and spectroscopically characterized a series of structurally closely related phthalocyaninato zinc(â…¡) complexes fused with different number and/or disposition of 15-crown-5 groups at the peripheral positions Zn(Pc')(1-6)[Pc'=Pc, Pc(15C5),Pc(opp-15C5)₂,Pc(adj-15C5)₂,Pc(15C5)₃,Pc(15C5)₄;Pc=unsubstituted phthalocyaninate;Pc(15C5) = 2,3-(15-crown-5)phthalocyaninate;Pc(opp-15C5)₂ = 2,3,16,17-bis(15-crown-5)phthalocyaninate;Pc(adj-15C5)₂ = 2,3,9,10-his(15-crown-5)phthalocyaninate;Pc(15C5)₃ = 2,3,9,10,16,17-tris(15-crown-5)phthalocyaninate;Pc(15C5)₄ = 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninate].The effect of number and dispositions of 15-crown-5 moieties on their electronic and vibrational spectroscopic properties was understood by systematic investigation over the electronic absorption, infra-red(IR),and Raman spectra of this series of phthalocyaninato zinc complexes.In addition,density functional theory(DFT) and time-dependent density functional theory (TD-DFT) calculations were carried out to comparatively describe the molecular structures, atomic charges,electronic absorption spectra,infrared(IR),and Raman spectra of 1-6, revealing the nature of the main transitions in electronic absorption spectra and identifying the vibration modes in the IR and Raman spectra of the series of six complexes with the assistance of animated pictures produced on the basis of the normal coordinates.4.Density Functional Theory Study on the Semiconducting Properties of Metal Phthalocyanine Compounds:Effect of Axially Coordinated LigandThe semiconducting properties of a series of metal phthalocyanine complexes with axially coordinated ligand(s) including F₂SnPc,Cl₂SnPc,I₂SnPc,OSnPc,OVPc,and Cl₂TiPc have been systematically investigated by density function theory(DFT) calculations.The intrinsic electron mobility(μ-) is revealed to be 0.045,0.13,and 0.0056 cm² V^-1 s^-1,respectively,for Cl₂SnPc,I₂SnPc,and Cl₂TiPc.Comparative studies with unsubstituted counterpart SnPc reveal the effect of axially coordinated electron-withdrawing ligands on the semiconducting properties.Introduction of the axially coordinated electron-withdrawing ligands onto SnPc is revealed to lower the HOMO and LUMO energy level and increase the ionization energy and electron affinity,resulting in the change in semiconductor nature from p-type to n-type. The present work,representing the first theoretical effort on studying the semiconducting properties of a series metal phthalocyanine complexes with axially coordinated ligand(s), should be helpful for understanding the OFET properties of phthalocyanine derivatives as well as designing and preparing novel phthalocyanine semiconductors with good OFET performance.