Hypsochromic solvent shift of the charge separation band in ionic donor–acceptor Li⁺@C₆₀⊂[10]CPP

Abstract

Photoinduced electron transfer in CPP-based donor–acceptor complexes C60⊂[10]CPP and Li+@C60⊂[10]CPP was studied using DFT/TDDFT. Unusual blue shift of charge separated states for Li+@C60⊂[10]CPP complexes in the polar medium is predicted.

Triquinoline‐ versus Fullerene‐Based Cycloparaphenylene Ionic Complexes: Comparison of Photoinduced Charge‐Shift Reactions

“…As noted above, TQ⋅H + ⊂[12]CPP and Li + @C 60 ⊂[10]CPP complexes exhibit some similarity in structural and electronic properties. The hypsochromic solvent shift of the CSh band found in Li + @C 60 ⊂[10]CPP has been attributed to the ability of the subunits to distribute the charge uniformly over the entire fragment . Since [10]CPP is larger than Li + @C 60 , the final state of the ET reaction, Li@C 60 ⊂[10]CPP + , has a smaller solvation energy than the initial state Li + @C 60 ⊂[10]CPP.…”

“…The hypsochromics olvents hift of the CSh band found in Li + @C 60 & [10]CPP has been attributed to the ability of the subunits to distribute the charge uniformly over the entire fragment. [20] Since [10]CPP is larger than Li + @C 60 ,t he final state of the ET reaction, Li@C 60 &[10]CPP + ,h as as maller solvation energy than the initial state Li + @C 60 & [10]CPP.I nT Q•H + & [12]CPP,h owever,w eo bserve ab athochromic shift of the CSh band. Comparison of molecular orbitals (MOs) representing the CSh states in TQ•H + and Li + @C 60 allows us to explain the qualitative difference in the solvente ffects.…”

“…The substantial changes in MEP on [12]CPP are due to inefficient delocalization of the positive charge over the unit, related to the large dihedrala ngles between phenyl groupso f [ 12]CPP in TQ•H + & [12]CPP.I nc ontrast, the MEP changes around [ 10]CPP in the Li + @C 60 & [10]CPP complex are small due to strong delocalization of the positive charge. [20] Thus, the different charged elocalization over the CPP units is the crucial factor determining the opposite solvatochromic shift in Li + @C 60 & [10]CPP and TQ•H + & [12]CPP.…”

“…The electrochemicala nd spectroscopic measurements revealed as trong charge-transfer interaction between [10]CPP and Li + @C 60 .I ts charge transfer (CT) absorption band demonstrates as olvent-induced blueshift due to destabilization of the charge-separateds tate by polar medium. [20] Since this complex is structurally similart oT Q•H + & [12]CPP, onec an expect that TQ•H + & [12]CPP and other TQ•H + based complexes can also exhibit photoinduced electron transfer (PET) properties. We notet hat presumably diquinolinea nd substituted triquinolines can be used insteado f TQ•H + as an electron acceptor in complexesw ith [ 12]CPP.I n this context,t he resemblance and distinctions in the photochemicalbehavior of TQ•H + and Li + @C 60 are of interest.…”

“…The electrochemical and spectroscopic measurements revealed a strong charge‐transfer interaction between [10]CPP and Li + @C 60 . Its charge transfer (CT) absorption band demonstrates a solvent‐induced blueshift due to destabilization of the charge‐separated state by polar medium . Since this complex is structurally similar to TQ⋅H + ⊂[12]CPP, one can expect that TQ⋅H + ⊂[12]CPP and other TQ⋅H + based complexes can also exhibit photoinduced electron transfer (PET) properties.…”