Two inorganic–organic hybrid materials based on polyoxometalate anions and methylene blue: Preparations, crystal structures and properties

Manifestation of intermolecular interactions in FTIR spectra of methylene blue molecules

“…Unlike the case of Fig. 5b, H In the case of dimer formation, the distance between the MB molecules was about 3.0 Å, which indicates the occurrence of π-π stacking interactions between the aromatic rings of the dye molecules [20]. Table 1 1) The band of the C het =N + (CH 3 ) 2 vibrations (1640-1650 cm -1 ) was observed only for the samples containing a significant fraction of MB monomers (10 -6 -10 -5 mol/L).…”

“…4, curves 2, 3). We came to conclusion on the contribution of π-π stacking interactions between the aromatic rings of MB in the formation of dimers and H-aggregates of MB [16,19,20,41,42]. [7,32,39].…”

“…Thus, the IR spectrum of free MB molecules should be clarified. The significant π-π interaction between the aromatic rings of MB heterocycles was supported by estimations of interplanar distance of the forming dimers [16,19,20]. In a theoretical work [39] it was shown that the strongest interaction of π system of MB heterocycle was the bond for which water plays a role of protonacceptor.…”

“…In MB case they are hydrochlorides. In such cases it is important to take into account the effect of intermolecular interactions in dye-dye and dye-environment systems [8,13,[16][17][18][19][20][39][40][41][42][43][44].…”

“…According to some ideas during the self-association of dyes, dimers and H-aggregates are formed due to dipole-dipole interactions of powerful π-electron clouds of molecules [16,19,20,41,42]. Another view is that the self-association is determined by hydrogen bonding [39,43,44].…”