Topochemical solid state photodimerization of non-ideally oriented monomers: 7-chlorocoumarin and 7-methoxycoumarin

6,7,8-Trimethoxycoumarin fromCryptocarya bracteolata

“…1). The compound complements the list of coumarins having methoxy (and/or hydroxy) groups in the 5 to 8 positions of the coumarin fused-ring, i.e., 6-methoxy- (Bauers et al, 2002;Gnanaguru et al, 1985), 7-methoxy- (Bhadbhade et al, 1984;Gnanaguru et al, 1984;Gnanaguru et al, 1985;Ramasubbu, et al, 1981;Ramasubbu et al, 1982), 8-methoxy- (Baures et al, 2002;Gnanaguru et al, 1985), 5,7-dimethoxy- (Ye & Fan, 2007), 7-hydroxy-6-methoxy- (Kimura et al, 1980), 7-hydroxy-5,6-dimethoxy- (Wagner et al, 1974) and 7-hydroxy-6,8-dimethoxy- (Li et al, 2001) coumarins.…”

“…For the crystal structures of coumarins having methoxy (and/or hydroxy) groups in the 5 to 8 positions, see: Baures et al (2002); Bhadbhade et al (1984); Gnanaguru et al (1984Gnanaguru et al ( , 1985; Kimura et al (1980); Li et al (2001); Ramasubbu et al (1981Ramasubbu et al ( , 1982; Wagner et al (1974); Ye & Fan (2007).…”

Monitoring structural transformations in crystals. 5. A topotactic [2 + 2]-photodimerization reaction

“…In the past decade interest in photo-induced reactions in crystals has increased signi®cantly because of the development of modern technologies and selective organic syntheses. Nevertheless, crystallographic studies of photochemical reactions were usually limited to a comparison of structures of pure substrate and pure product crystals (Anderson et al, 1979;Chung et al, 1991;Ehrenberg, 1968;Gnanaguru et al, 1984Gnanaguru et al, , 1985Guru Row et al, 1983;Harada et al, 1995Harada et al, , 1996Ohhara et al, 2000;Suzuki et al, 1994;Theocharis et al, 1981;Wang & Jones, 1987). In some cases the structures of mixed objects, containing both the substrate and the product, were reported (Chang et al, 1987;Enkelmann et al, 1993;Harada et al, 1999;Kawano et al, 1999;Leibovitch et al, 1998;Nakanishi et al, 1981;Novak et al, 1993a,b;Theocharis, Desiraju & Jones, 1984).…”

Molecular structures and crystal packings of 2-styrylquinoxaline derivatives

“…Note that, in the excited state, the strength of the π orbital interaction in the dimer is more important for the implementation of PCA than geometric parameters [27][28][29][30][31]. In all cases of implementation of the PCA reaction in the crystals with distances between the ethylene groups exceeding the Schmidt criterion, a strong π orbital interaction in the dimer was noted in the excited state.…”