Photochemical and photophysical properties of aza[6]helicenes synthesized via EDA complex initiated visible-light-mediated photocyclization

Photochemical and photophysical properties of aza[6]helicenes synthesized via EDA complex initiated visible-light-mediated photocyclization Full article

Journal

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
ISSN: 1386-1425 , E-ISSN: 1873-3557

Output data

Year: 2026, Volume: 363, Article number : 128406, Pages count : 15 DOI: 10.1016/j.saa.2026.128406

Tags

Photocyclization, Aza[6]helicenes, Fluorescence, Acidochromism, Photoprotonation, Singlet oxygen

Authors

Tamozhnikova Veronica S. ¹ , Mekeda Igor S. ² , Balakhonov Roman Yu. ² , Ershov Kirill S. ¹ , Baklanov Alexei V. ¹ , Buravlev Alexander A. ^3,4 , Glebov Evgeni M. ^1,4 , Shirinian Valerii Z. ²

Affiliations

1	V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str., 630090 Novosibirsk, Russian Federation
2	N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47, Leninsky Prosp., Moscow 119991, Russian Federation
3	N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, 9 Lavrentiev Prosp., 630090 Novosibirsk, Russian Federation
4	Novosibirsk State University, 2 Pirogova Str., 630090 Novosibirsk, Russian Federation

We have synthesized three new six-membered fluorescent azahelicenes of naphthofuroquinoline (NFQ) series via blue LED-induced and electron donor–acceptor (EDA) complex mediated photocyclization of 1-naphthyl naphtho[2,1-b]furans. The concise and effective photochemical approach to the synthesis of aza[6]helicenes (Hel) was made possible by the ability of the starting naphthofuran acyl oxime to form EDA complexes with tertiary amines. Performed synthetic studies and 1H NMR monitoring showed that acyl oximes of the naphthofuran series form a very effective EDA complex with diazabicyclo(5.4.0)undec-7-ene (DBU) with a bathochromic shift of the absorption band, which opens the possibility of using blue LED radiation for their photocyclization. The photophysical and photochemical properties of Hels in typical organic solvents were described. Both electronic absorption and fluorescence spectra were found to be acid-dependent. In the most interesting case of 8-(4-(trifluoromethyl)phenyl)benzo[f]naphtho[1′,2′:4,5]furo[2,3-c]quinolone in CH3CN, the fluorescence quantum yield is modulated by acidification from moderate (25%) to quite high (63%). Acidochromism in the presence of trifluoroacetic acid is caused by the formation of two successive complexes, [HelH+…CF3COO−] and [HelH+…CF3COO−…CF3COOH]. The equilibrium constants are determined. Hels are photochemically stable in chlorine-free solvents. In chloroform and dichloromethane (DCM) photoprotonation was observed, occurring from both singlet and triplet excited states. The studied helicenes promoted the formation of singlet oxygen in acetonitrile solutions with a moderate (30–40%) quantum yield.

Tamozhnikova V.S. , Mekeda I.S. , Balakhonov R.Y. , Ershov K.S. , Baklanov A.V. , Buravlev A.A. , Glebov E.M. , Shirinian V.Z.
Photochemical and photophysical properties of aza[6]helicenes synthesized via EDA complex initiated visible-light-mediated photocyclization
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2026. V.363. 128406 :1-15. DOI: 10.1016/j.saa.2026.128406 OpenAlex

Submitted:	Mar 12, 2026
Accepted:	Jul 7, 2026
Published print:	Jul 8, 2026
Published online:	Jul 13, 2026

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