Abstract: A series of polyhalogenated hetarylamines and their co-crystals with 18-crown-6 ether was used to reveal the effect of co-crystallization on the supramolecular structure and fluorescence properties as well as the relationship between these characteristics and peculiarities of the hetarylamine chemical structure (alpha- or gamma-position of the NH2 group, number of Cl and F substituents, pyridine or quinoline framework, presence of a fluorophore fragment). Incorporation of crown ether into the crystal matrix of the hetarylamine results in a significant rearrangement of the supramolecular structure. In all cases, the N-HMIDLINE HORIZONTAL ELLIPSISNhet and N-HMIDLINE HORIZONTAL ELLIPSISF H-bonds are replaced by the N-HMIDLINE HORIZONTAL ELLIPSISOcrown bond. Changes in pi-electron interactions that affect fluorescence characteristics depend on the amine structure. In the co-crystals of gamma-aminopyridines, replacement of C-FMIDLINE HORIZONTAL ELLIPSIS pi(F) interactions with pi FMIDLINE HORIZONTAL ELLIPSIS pi(F) stacking causes the fluorescence quenching or a bathochromic shift of lambda(em), whereas replacement of pi FMIDLINE HORIZONTAL ELLIPSIS pi(F) or pi FMIDLINE HORIZONTAL ELLIPSIS pi(H) stacking with C-FMIDLINE HORIZONTAL ELLIPSIS pi(F) interactions or pi HMIDLINE HORIZONTAL ELLIPSIS pi(H) stacking in the co-crystals of alpha-aminopyridines is accompanied by the hypsochromic shift of lambda(em). gamma-Aminopyridines show more pronounced changes in fluorescence characteristics as compared to alpha-aminopyridines, the effect being dependent on the nature of the halogen substituents. The fluorescence properties of aminoquinolines, regardless of the amino group location, are insignificantly modified due to the ability of the extended pi-system to minimize interaction changes. Exploration of the nature of the excited states of isolated molecules, homocrystals and co-crystals using quantum mechanical calculations evidences that fluorescence quenching occurs due to EET, facilitated by the presence of crown ether molecules. The bathochromic and hypsochromic shifts of emission are caused by the change in a mutual orientation of the hetarylamine molecules with subsequent different stabilization of the ground and excited states. Using DSC, the co-crystals' supramolecular structure was found to self-organize from solution or melt and to regenerate in the melting-crystallization cycle. The revealed modification of the hetarylamines' fluorescence properties due to the formation of co-crystals with crown ether seems to be promising for use in solid-state supramolecular chemo and thermo sensors (indicators).

Cite: Vaganova T.A. , Gatilov Y.V. , Benassi E. , Chuikov I.P. , Pishchur D.P. , Matykhin E.V.
Impact of molecular packing rearrangement on solid-state fluorescence: polyhalogenated N-hetarylamines vs. their co-crystals with 18-crown-6
CrystEngComm. 2019. V.21. N39. P.5931-5946. DOI: 10.1039/c9ce00645a WOS Scopus РИНЦ OpenAlex

Identifiers:

Web of science:	WOS:000489243300008
Scopus:	2-s2.0-85073187272
Elibrary:	41693478
OpenAlex:	W2969485981

Citing:

DB	Citing
Web of science	15
Scopus	15
Elibrary	15
OpenAlex	16

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