Impact of molecular packing rearrangement on solid-state fluorescence: polyhalogenatedN-hetarylaminesvs.their co-crystals with 18-crown-6

Abstract

Relationship between the hetarylamine chemical structure, crystal packing in homo- and co-crystals, and fluorescence effects (quenching, bathochromic and hypsochromic shifts).

Polyhalogenated aminobenzonitrilesvs.their co-crystals with 18-crown-6: amino group position as a tool to control crystal packing and solid-state fluorescence

“…Thus, changes in the solid-state fluorescence upon cocrystallization with 18-crown-6 are similar to those observed in the case of polyhalogenated N-hetarylamines 17 despite the fact that the CN group in the aromatic co-former affects the parameters of p-π electron interactions, geometry of stacked pairs and crystal packing in general. The data obtained on the aminobenzonitrile and aminopyridine series indicate that mutual arrangement of the H-bond acceptor function, i.e.…”

“…The arylamine molecules are disposed on both sides of the macrocycle plane and are coordinated by the H-bond N-H⋯O cr typical for the co-crystals of 18-crown-6 with polyhalogenated (hetero) aromatic mono-and diamines. 16,17,56,57 Table S2 † presents the parameters of the H-bonds. π-Electron interactions of the aromatic molecules, i.e.…”

“…The structure of the 1D assemblies in D 2 •cr and E 2 •cr co-crystals on the whole is similar to that in the cocrystals of cr with polyhalogenated (hetero)arylamines. 16,17 However, a significant difference due to the CN group directed to the periphery of the assemble is revealed: aminobenzonitrile molecules in the adjacent chains are connected by linear CN⋯Cl contact to form a layered 2D structure in the co-crystals (Table 1, Fig. 3b and S1c †).…”

“…Thermocycling of A 2 •cr and D 2 •cr leads to quite noticeable changes in the thermal effect in the second melt. However, such differences in the DSC parameters of co-crystals upon thermocycling were observed in some cases 16,17,73 and appear to be caused by normalization or quenching of the sample without any change in the crystal structure. In particular, crystallographic data obtained 16 on the A 2 •cr single crystals prepared from a solution and from a melt indicate the identity of the crystal structure despite the large differences in the thermal characteristics.…”

“…For the purpose of understanding and controlling the effects of co-formers' structure on the crystal packing and photophysical properties (fluorescence), systematic investigations based on series of compounds with variable parameters are required. In our previous work 17 we used a series of polyhalogenated N-hetarylamines and their cocrystals with 18-crown-6 to reveal the relationships between the hetarylamine chemical structure (α-or γ-position of the NH 2 group, number of Cl and F substituents, pyridine or quinoline framework), molecular packing transformations and fluorescence changes. This study showed that the αand γ-amino derivatives exhibit counter-directional photophysical effects when co-crystallized with crown ether: an increase of the π-interaction energy in γ-amine pairs is accompanied by a bathochromic shift of λ em or fluorescence quenching, and weakening of π-electron interactions between α-amine molecules results in a hypsochromic shift.…”