In Search of Excited-State Proton Transfer in the Lumichrome Dimer in the Solid State:  Theoretical and Experimental Approach

Abstract

Quantum chemical density functional theory (DFT) calculations and spectral data were employed to investigate the possibility of the excited-state double proton transfer (ESDPT) in lumichrome crystals. The calculations in a lumichrome dimer predict a transfer of a proton in the first excited state, leading to a cation-anion pair. The presently reported X-ray structure of 1,3-dimethyllumichrome and its complex solid-state luminescence indicate that also in this molecule intermolecular hydrogen bonds might be involved in the photophysics. The long-wavelength emission in lumichrome crystals peaked at 530 nm is attributed to excited-state proton transfer, whereas a wider emission band in methylated lumichrome derivatives peaked at 560 nm is attributed to ions formed upon photoexcitation of the crystals.

Local dipole interactions induce helicity of (S)-2-butyl-N-(1,8-naphthaloyl)-2-aminobenzoate molecules containing 1,8-naphthalimide rings utilized as a column building blocks: X-ray and quantum mechanical studies

“…For example, we have demonstrated that interactions between parallel and antiparallel local dipoles are responsible for mutual orientation of oxalamide molecules [30], while the presence of a new type of a weak bond between oxygen atom from carbonyl moiety and carbon atom within aromatic ring governs the behavior of imidazopyridine derivatives [31]. Similarly, combined quantum mechanical and X-ray investigations appeared successful in studies on grid-type complexes [32] and double proton transfer in lumichrome dimers [33]. A series of computational and experimental studies allowed us to provide the reasons favoring conformations of drugs fulvastatin [34], azathioprine [35], and other purines [36], as well as (R,R)-tartaric acid esters [37], amides [38], nitriles [39], or deoxyfluoro derivatives [40].…”

Surface photochemistry: alloxazine within nanochannels of Na+ and H+ ZSM-5 zeolites

“…Such an interpretation is based on an analogy to the results of earlier studies of lumichrome using luminescence experiments, DFT calculations and X-ray results in ref. 30 and references cited therein. Note that this anion is believed to be deprotonated at N 1 position, thus the emission at 540 nm can be assigned to the N 3 anion.…”

“…As previously reported, alloxazine dimers are the origin of the isoalloxazine-type emission. 30,31 The published approximate dimensions of the intersections are 9 A ˚32 and, as Scheme 3 shows, the alloxazine dimer may fit into that cavity.…”

Photophysics of lumichrome in anionic and cationic micellar media

“…22,23 LCM is the major product of photodecomposition of riboavin (vitamin B 2 ) under neutral or acidic pH. Using quantum mechanical calculation, Sikorski et al 24 found an excited state double proton transfer (ESDPT) occurs in the LCM dimer in the solid state. A different type acid-base equilibrium of LCM at different pH values suggested the existence of different species LCM such as neutral species (DMAL and DMIS), two monoanions, and one dianion species.…”