Derivatives of 2 styrylquinoline (2SQ), due to their photochemical activity, are used to simulate the action of photonic molecular switches and logic gates [1][2][3][4][5]. Photoisomerization quantum yields of these com pounds can reach values of 0.5 and above, but their disadvantage is relatively small fluorescence quantum yields (ϕ fl ), not exceeding a few hundredths [6]. To address this shortcoming, it is necessary to pass to het erodiarylethylenes, which possess pronounced fluo rescent properties (ϕ fl > 0.1), but it is important that the photoactivity of the compounds, that is, ability to photoisomerization, should persist. For example, when passing from 2SQ to the bis quinoline derivative of distyrylbenzene the ϕ fl value increases significantly (up to 0.63), but the quantum yield of the trans-cis photoisomerization reaction of the first double bond EE → ZE decreases steeply (down to 0.03), and the trans-cis photoi somerization reaction of the second double bond ZE → ZZ does not occur [7].It is known that the angular annulation of the quin oline nucleus, that is, passing from 2SQ to 3 styryl benzo[f]quinoline (3SBQ), leads to a significant increase in the fluorescence quantum yield up to 0.74, with the quantum yield of trans-cis photoisomeriza tion retaining a fairly high value (ϕ tc = 0.19), and the quantum yield of the reverse reaction of cis-trans pho toisomerization ϕ ct = 0.38 [8].Note that photoswitchable fluorophores are "real chemical basis" of one of the methods of ultrahigh res olution fluorescent microscopy ("nanoscopy") [9-11], for the development of which the Nobel Prize in Chemistry was awarded in 2014.To find out photochromes of the class of heterodi arylethylenes, being also fluorophores, that is, satisfy ing the conditions ϕ tc > 0.1 and ϕ fl > 0.1, we studied in this work a number of 3SBQ derivatives: trans 3 (3 methoxystyryl)benzo[f]quinoline (3MSBQ), trans 3 (4 methoxystyryl)benzo[f]quinoline (4MSBQ), and trans 3 (4 methoxycarbonylstyryl)benzo[f]quinoline (4MCSBQ) (Scheme 1): N N PHOTOCHEMISTRY Abstract-The spectral, luminescent, and photochemical properties of 3 styrylbenzo[f]quinoline (3SBQ)derivatives containing methoxy and methoxycarbonyl groups have been studied. All of these compounds luminesce in the region of 380-480 nm with quantum yields up to 0.74 and undergo reversible photoisomer ization with quantum yields of 0.2-0.5. It has been found that compounds with a methoxy group at the meta position and a methoxycarbonyl group at the para position of the styryl moiety are unstable photochromes and also undergo other photochemical reactions side relative to photoisomerization. The absorption spectra of the two 3SBQ s conformers calculated by the density functional theory (DFT) method (TD B3LYP/6 31G*) describe well the experimental spectrum. The analysis of the structures of molecular orbitals and tran sitions between them has made it possible to explain the observed effects of substituents on the absorption spectrum of 3SBQ.