The Factors Affecting Charge Transport And The Excited-state Proton Transfer Of Multiple-Ring Molecule

In this work,density functional theory(DFT),time-dependent density functional theory(TDDFT)and spectra experiments are employed to investigate factors affecting the carrier mobility of organic semiconductor materials and reaction mechanism of excited-state proton transfer(ESPT)of various multiple number-membered ring hydrogen bonding molecular system.Main research contents and related conclusions are as follows:(1)Combining the first principle calculation with Marcus theory,we study effects of alkyl substitution and N,O,S elements on the carrier mobility of organic semiconductor materials.Firstly,we compare the reorganization energy,electronic coupling and intermolecular distance of bistetracene(BT)before and after alkyl substitution.We find that alkyl substitution has little effect on molecular reorganization energy,while can enhance intermolecular electronic coupling,and the carrier mobility is also improved.Subsequently,we select the N,N'-dioctyl-NDTI(C8-NDTI)molecule containing N,O,S elements in the structure.Comparing the contribution of N,O,S elements to the reorganization energy,bond length and molecular orbital,respectively,we find that O atom can effectively reduce the reorganization energy and increase the electronic coupling in the hole transfer process;S atom can weaken the reorganization energy of the charge transfer process;while N atom has no obvious effect on both the charge and hole transfer processes.(2)Based on the TDDFT methods,we investigate the ESPT process of five-membered-ring intrmolecular hydrogen-bonding 2-(6'-hydroxy-2'-pyridyl)benzimidazole(BI)in acetonitrile,water and ethanol solvents,respectively.Based on the geometric optimization and potential curve analysis,in the aprotic acetonitrile solvent,we find that there exists an uncrossable barrier(18 kcal/mol)of BI in both the ground state and the excited state.In other words,BI in acetonitrile solvent cannot undergo excited intramolecular proton transfer(ESIPT)reaction.Subsequently,we construct the intermolecular hydrogen bond between BI and solvent molecule by using a water or an ethanol molecule as proton transfer bridge.By scanning and optimizing the two intermolecular hydrogen bonds,we find that BI can cross the small barrier(7?9 kcal/mol)to occur the ESPT reaction with the assistance of water and ethanol molecules.The stepwise ESPT reaction mechanism of BI is also confirmed in water and ethanol solvents.(3)Using a variety of functionals,we study the excited state intramolecular double proton transfer(ESIDPT)reaction of doxorubicin(DXR)molecule containing two six-membered-ring intramolecular hydrogen bonds.Firstly,we simulate the fluorescence spectra of DXR and find two unobservable fluorescence peaks(578 nm and 572 nm)in the experiment,assigning to two single proton transfer isomers.Then,analyzing the potential energy curves,we find that DXR can occur ESIDPT reaction along two continuous single proton transfer paths,and the two proton transfer paths are competitive.Moreover,the ESIDPT mechanism of DXR in a synergistic manner is eliminated due to the high barrier.(4)We strategically design,synthesize and characterize a non-planar seven-membered-ring intramolecular hydrogen bonding 3-(2-(4-(dimethylamino)phenyl)b-enzothiazol-4-yl)-4-hydroxybenzonitrile(HBN)theoretically and experimentally.Analyzing the fluorescence spectrum observed in the experiment,we find that the ESIPT reaction of HBN can occur in water,but not in organic solvent.The subsequent potential energy surface analysis also prove that the ESIPT reaction of HBN can occur in water.In addition,we inhibit the ESIPT reaction by adding the cucurbituril[7]to the HBN solution,and the ESIPT reaction process of HBN was restore after adding the adamantane.Thus,we realize the regulation of cucurbituril[7]-adamantane on the ESIPT reaction process of HBN.