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SUMMARY:Effect of fluorination on the molecular electrostatic potential of
  itic non-fullerene acceptors
DTSTART;VALUE=DATE-TIME:20260922T142000Z
DTEND;VALUE=DATE-TIME:20260922T142500Z
DTSTAMP;VALUE=DATE-TIME:20260914T044843Z
UID:indico-contribution-537@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Mariia  Terebinska (Chuiko Institute of Surface Chem
 istry\, NAS of Ukraine)\nOrganic solar cells based on non-fullerene accept
 ors (NFAs) are a promising direction in the development of organic photovo
 ltaics due to the possibility of targeted molecular design and control of 
 their electronic and optical properties. Particular attention is paid to A
 –D–A-type acceptors\, including ITIC and its fluorinated derivatives\,
  for which the introduction of fluorine atoms provides an effective approa
 ch to modifying the electronic structure and electron-accepting properties
  of the molecules. In this work\, a quantum-chemical study of ITIC\, ITIC-
 2F\, and ITIC-4F molecules was performed using density functional theory (
 DFT) and time-dependent DFT (TD-DFT). Geometry optimizations were carried 
 out at the B3LYP/6-31G(d\,p) level\, followed by analysis of the electroni
 c structure\, frontier molecular orbitals (HOMO/LUMO)\, and molecular elec
 trostatic potential (MEP). It was found that sequential fluorination has a
  negligible effect on the molecular geometry. All studied systems retain a
 n almost planar π-conjugated structure\, with changes in the dihedral ang
 les not exceeding 0.12°. This indicates that the effect of fluorination o
 n the electronic properties is governed predominantly by electronic rather
  than structural factors.\nAnalysis of the frontier molecular orbitals sho
 wed that the HOMO is predominantly localized on the central donor IDTT cor
 e\, whereas the LUMO is mainly concentrated on the terminal acceptor fragm
 ents. Upon going from ITIC to ITIC-4F\, the HOMO energy decreases from −
 5.380 to −5.508 eV\, while the LUMO energy decreases from −3.309 to 
 −3.464 eV. The stabilization of the LUMO is more pronounced and is attri
 buted to the electron-withdrawing inductive effect of the fluorine atoms. 
 Particular attention was paid to the analysis of the molecular electrostat
 ic potential. The MEP maps show that\, for ITIC\, ITIC-2F\, and ITIC-4F\, 
 the most negative electrostatic potential is predominantly localized on th
 e terminal electron-accepting fragments\, particularly near the carbonyl g
 roups. In contrast\, the central conjugated core is characterized by a pre
 dominantly neutral or weakly positive potential.\nFluorination does not al
 ter the overall topology of the MEP distribution but systematically affect
 s its local intensity. For ITIC-2F\, an increase in the negative electrost
 atic potential is observed in the terminal acceptor regions\, while this e
 ffect becomes more pronounced for ITIC-4F. At the same time\, the central 
 part of the molecule becomes more positive\, indicating enhanced intramole
 cular polarization and redistribution of electron density from the central
  conjugated core toward the peripheral acceptor fragments.\nThus\, the MEP
  analysis (fig.) is consistent with the spatial distribution of the LUMO a
 nd confirms an enhanced electron-accepting character of the peripheral fra
 gments upon fluorination. The observed modification of the electrostatic p
 olarization may affect the nature of intermolecular interactions and charg
 e-transfer processes in ITIC-based molecular materials. The most pronounce
 d changes are observed for ITIC-4F containing four fluorine atoms.\n 	 	 \
 nFig. MEP mapped onto an electron density isosurface (ρ = 0.001 a.u.) for
  ITIC\, ITIC-2F\, and ITIC-4F molecules.\n\nhttps://indico.bitp.kiev.ua/ev
 ent/18/contributions/537/
LOCATION:Bogolyubov Institute for Theoretical Physics Conference Hall
URL:https://indico.bitp.kiev.ua/event/18/contributions/537/
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