Publication detail

Synthesis, photophysics and two-photon absorption of imidazole-centred tripodal chromophores

Year: 2024

Type of publication: článek v odborném periodiku

Name of source: Physical Chemistry Chemical Physics

Publisher name: Royal Society of Chemistry

Place: Cambridge

Page from-to: 20908-20918

Titles:

Language	Name	Abstract	Keywords
cze	Syntéza, fotofyzikální vlastnosti a dvoufotonová absorpce trojramenných chromofotrů s centrálním jádrem imidazolu	Byly připraveny trojramenné push-pull chromofory s 1-methyl-2,4,5-trifenyl-1H-imidazolem jako centrální donorní jednotkou. Byly studovány jejich termické, elektrochemické, fotofyzikální a nelineárně-optické vlastnosti a srovnávány s výsledky kvantově-chemických výpočtů. Syntetické kroky zahrnovaly Suzukiho-Miyaurovy a Knoevenagelovy reakce, centrální skelet byl dekorován periferními elektronakceptory jako formylovou, kyan, esterovou nebo trifluormethylskupinu nebo komplexnější fragmenty jako skelety odvozené od kyselin malonové nebo octové či indan-1,3-dion a rhodanin. Z důvodu substituce byla všechny tři ramena na centrálním jádře imidazolu více či méně vytočena z roviny. Centrální imidazol podléhá vratné jednoelektronové oxidaci, periferní akceptory jsou nevratně redukovány ve víceelektronovém procesu. Změřená absorpční spektra nevykazují závislost na rozpouštědle, naopak emisní spektra silně závisejí na polaritě rozpouštědla a síle elektronakceptorního působení periferního substituentu.	push-pull syst0m; chromofor; imidazol; dvoufotonová absorpce; nelinearní optické vlastrnosti
eng	Synthesis, photophysics and two-photon absorption of imidazole-centred tripodal chromophores	Tripodal push-pull chromophores with D-(pi-A)3 arrangement were synthesized using 1-methyl-2,4,5-triphenyl-1H-imidazole as a central electron donor, and their thermal, electrochemical, photophysical and non-linear optical properties were studied and corroborated with quantum-chemical calculations. Their facile synthesis involved Suzuki-Miyaura and Knoevenagel reactions, allowing the installation of various peripheral electron acceptors such as formyl, cyano, ester, trifluoromethyl and more complex moieties such as malonic/acetic acid derivatives, indan-1,3-dione and rhodanine. All phenyl rings appended at the central imidazole core were more or less twisted depending on the peripheral substitution. Although imidazole undergoes reversible one-electron oxidation, peripheral acceptors are reduced irreversibly in a multi-electron process. This behaviour is further seen as a variation of the LUMO, while the HOMO remained almost unaltered across the whole series. TD-DFT calculations revealed centrifugal charge transfer from the central imidazole to all C2, C4 and C5 branches occupied by the LUMO, LUMO+1 and LUMO+2. The HOMO-LUMO gap is tuneable within the range of 3.55-2.31 eV, while the longest-wavelength absorption/emission maxima were found within the broad range of 304-448/393-612 nm. Although the absorption spectra are solvent-independent, the emission depends strongly on the solvent polarity and the electron-withdrawing power of the peripheral acceptors. Extended chromophores with complex electron acceptors were investigated as two-photon absorbers, revealing relatively good cross-section values of up to 521 GM and a figure-of-merit (Phi F x delta 2PA) of around 190 GM. Tripodal imidazole-centred chromophores bearing peripheral acceptors were prepared and investigated. The observed centrifugal ICT results in tuneable (nonlinear) optical properties and two-photon absorption cross-sections of up to 521 GM.	push-pull system; chromophore; imidazole; two-photon absorption; non-linear optics

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