Highly Regioselective Solid-State Photodimerization of Naphthoquinolizinium Salts

Abstract

Keywords: Cycloadditions / Heterocycles / π interactions / Photochemistry / Solid-state reactionsThe photodimerization of benzo-annellated acridizinium derivatives, namely naphtho[1,2-b]quinolizinium and naphtho[2,1-b]quinolizinium bromide, has been investigated in solution and in the solid state. Irradiation of the naphthoquinolizinium salts in solution gave all possible regioisomers in an unselective [4+4] photocycloaddition reaction. In contrast, the irradiation of crystalline samples resulted in regioselective dimerization to give the anti-head-to-tail photodimers.

Approaching Two‐Dimensional Copolymers: Photoirradiation of Anthracene‐ and Diaza‐Anthracene‐Bearing Monomers in Langmuir Monolayers

“…[ 19 ] Regarding photoirradiation, which is of particular interest to the present publication, monomers M1 and M2 (Figure 1 a,b) were used to create the corresponding sheets S1 and S2 , respectively. Growth in these cases was mediated through dimerization of the monomers' anthracene (A) [20][21][22][23] and 1,8-diaza-anthracene (DAA) [24][25][26][27] units, respectively (Figure 1 c). The interfacial area used for polymerization is then the upper bound for the expanse of sheets S1 and S2 , being aware of the well-studied phenomenon of domain formation and its potentially detrimental impact on molecular structure when connecting the molecules on the macroscopic length scale.…”

“…a) Macrocycle M1 and b) macrocycle M2 used as monomers for copolymerization. c) Dimerization reactions of anthracene (A) and diaza‐anthracene (DAA) moieties leading to homodimers (top and center) and heterodimer (bottom) reported in the literature . Note that dimerizations of the A and DAA units of monomers M1 and M2 at the interface are likely to take place in the thermodynamically less favored syn fashion due to the orientation of the amphiphilic monomers at the air/water interface with all A and DAA units pointing more or less upwards.…”

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

“…2, Table 1). In water, the absorption essentially resembles the one of the parent naphthoquinolizinium ion, namely a structured absorption band was observed with a long-wavelength absorption maximum at 398 nm [45]. In all other tested solvents, this absorption band was also observed, however, in some cases less structured, along with an additional very broad red-shifted absorption band with maxima ranging from 447 nm (EtOH) to 465 nm (MeCN).…”

“…Notably, the isosbestic points confirm the exclusive presence of the two absorbing species 2 and 2 cB in the prototropic equilibrium. Based on the absorption and emission spectra in aqueous buffer, methanol and acetonitrile solution upon addition of acid or base, the blue-shifted absorption and emission bands, that essentially resemble the ones of the parent compound [45], are assigned to hydroxynaphthoquinolizinium 2 . In turn, the strongly red-shifted broad absorption and emission bands correspond to the conjugate base 2 cB .…”

Synthesis of Shape‐Persistent Macrocycles with Three 1,8‐Diazaanthracene Units and Their Packing in the Single Crystal

“…Light‐induced dimerization via [4+4]‐cycloaddition has been studied in great detail particularly for homoaromatic anthracenes and used for the creation of complex compounds1, 4 and polymers5 derived from simple components presenting one or more of these units. Substituted As tend to furnish anti dimers and aza‐, as well as diazaanthracenes (DAA), have an even stronger anti ‐preference 2b. 3, 6 Recently, we have started a program aiming at exploring shape‐persistent macrocyclic compounds7 with two or three A or DAA units for their ability to give polymers by photochemical treatment, both in the solid state and at the air/water interface.…”