TY - JOUR

T1 - Polyhalogenated aminobenzonitriles vs. their co-crystals with 18-crown-6: amino group position as a tool to control crystal packing and solid-state fluorescence

AU - Vaganova, Tamara A.

AU - Benassi, Enrico

AU - Gatilov, Yurij

AU - Chuikov, Igor P.

AU - Pishchur, Denis P.

AU - Malykhin, Evgenij

N1 - Funding Information: Analytical and spectral measurements were performed at the Multi-Access Chemical Service Centre SB RAS. The computational part of this work was carried out using the equipment kindly provided by the Siberian Supercomputer Centre (SSCC) ICMMG SB RAS. The technical personnel are also gratefully thanked. This research was supported by the Ministry of Science and Higher Education of the Russian Federation (project AAAA-A21-121011490017-5). DP acknowledges the support by the Ministry of Science and Higher Education of the Russian Federation (project 121031700313-8). Publisher Copyright: © The Royal Society of Chemistry.

PY - 2022/2/7

Y1 - 2022/2/7

N2 - A series of para- and ortho-aminobenzonitriles differing in the nature and number of halogen substituents were used to synthesize 2:1 co-crystals with 18-crown-6 ether. The supramolecular structure of the obtained co-crystals as well as aminobenzonitrile crystals was studied in detail using single-crystal X-ray diffraction. Incorporation of the crown ether into the crystal matrix of arylamine results in the replacement of the H-bonds between amine molecules (N-H⋯NC and N-H⋯F) by the bond with a crown oxygen atom (N-H⋯Ocr). The crystal packing rearrangement modifies the π-electron interactions between aminobenzonitrile molecules both in the type of contact (C-F⋯π, C-Cl⋯π, CN⋯π, π⋯π) and mutual arrangement of the stacked molecules (parallel/anti-parallel, displaced/rotated). These transformations cause a change in the solid-state fluorescence characteristics of aminobenzonitriles: co-crystallization is accompanied by a bathochromic shift of the fluorescence maximum in the case of para-isomers and by a hypsochromic shift in the case of ortho-isomers; the magnitude of this effect depends on the number of halogen substituents. Exploration of the nature of the intra- and intermolecular interactions, along with the excited states of the molecules in the gas phase, in aminobenzonitrile crystals and their co-crystals, using state-of-the-art TD-DFT calculations evidences that, depending on the NH2 group position, insertion of the crown ether causes either an increase in the change of the dipole moment upon photo excitation/emission with a subsequent increase in the Stokes shifts (para-aminobenzonitriles) or a decrease in these characteristics (ortho-aminobenzonitriles). This is consistent with the strengthening or weakening of π-electron aggregation in pairs of para- or ortho-aminobenzonitrile molecules, respectively, upon co-crystallization. A quantitative model that can clearly distinguish the different behaviours of ortho- and para-substituted molecules and provides an analytical tool of wide-ranging validity was proposed. The central importance of the mutual arrangement of the functions playing the role of the H-bond donor and acceptor was established; this finding may be exploited as a design tool to purposefully modify the molecular packing and tune the solid-state photophysical properties. Using DSC, the co-crystals' structure was found to self-organize in the same way upon crystallization from solution and from the melt and to regenerate in the melting-crystallization cycle. This journal is

AB - A series of para- and ortho-aminobenzonitriles differing in the nature and number of halogen substituents were used to synthesize 2:1 co-crystals with 18-crown-6 ether. The supramolecular structure of the obtained co-crystals as well as aminobenzonitrile crystals was studied in detail using single-crystal X-ray diffraction. Incorporation of the crown ether into the crystal matrix of arylamine results in the replacement of the H-bonds between amine molecules (N-H⋯NC and N-H⋯F) by the bond with a crown oxygen atom (N-H⋯Ocr). The crystal packing rearrangement modifies the π-electron interactions between aminobenzonitrile molecules both in the type of contact (C-F⋯π, C-Cl⋯π, CN⋯π, π⋯π) and mutual arrangement of the stacked molecules (parallel/anti-parallel, displaced/rotated). These transformations cause a change in the solid-state fluorescence characteristics of aminobenzonitriles: co-crystallization is accompanied by a bathochromic shift of the fluorescence maximum in the case of para-isomers and by a hypsochromic shift in the case of ortho-isomers; the magnitude of this effect depends on the number of halogen substituents. Exploration of the nature of the intra- and intermolecular interactions, along with the excited states of the molecules in the gas phase, in aminobenzonitrile crystals and their co-crystals, using state-of-the-art TD-DFT calculations evidences that, depending on the NH2 group position, insertion of the crown ether causes either an increase in the change of the dipole moment upon photo excitation/emission with a subsequent increase in the Stokes shifts (para-aminobenzonitriles) or a decrease in these characteristics (ortho-aminobenzonitriles). This is consistent with the strengthening or weakening of π-electron aggregation in pairs of para- or ortho-aminobenzonitrile molecules, respectively, upon co-crystallization. A quantitative model that can clearly distinguish the different behaviours of ortho- and para-substituted molecules and provides an analytical tool of wide-ranging validity was proposed. The central importance of the mutual arrangement of the functions playing the role of the H-bond donor and acceptor was established; this finding may be exploited as a design tool to purposefully modify the molecular packing and tune the solid-state photophysical properties. Using DSC, the co-crystals' structure was found to self-organize in the same way upon crystallization from solution and from the melt and to regenerate in the melting-crystallization cycle. This journal is

KW - INTRAMOLECULAR CHARGE-TRANSFER

KW - SUPRAMOLECULAR STRUCTURE

KW - DENSITY FUNCTIONALS

KW - EXCITED-STATES

KW - HYDROGEN-BONDS

KW - MP2 ENERGY

KW - APPROXIMATION

KW - DERIVATIVES

KW - EMISSION

KW - ATOM

UR - http://www.scopus.com/inward/record.url?scp=85124225836&partnerID=8YFLogxK

U2 - 10.1039/d1ce01469b

DO - 10.1039/d1ce01469b

M3 - Article

VL - 24

SP - 987

EP - 1001

JO - CrystEngComm

JF - CrystEngComm

SN - 1466-8033

IS - 5

ER -