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Structure-mechanical property correlations in mechanochromic luminescent crystals of boron difluoride dibenzoylmethane derivatives.

Krishna GR, Devarapalli R, Prusty R, Liu T, Fraser CL, Ramamurty U, Reddy CM - IUCrJ (2015)

Bottom Line: In contrast, both BF2dbm(OMe)2 and BF2dbmOMe are considerably stiffer and harder with comparable E and H, which are rationalized through analysis of the structural attributes such as the intermolecular interactions, slip systems and their relative orientation with respect to the indentation direction.As expected from the qualitative mechanical behaviour, prominent ML was observed in BF2dbm( (t) Bu)2, whereas BF2dbm(OMe)2 exhibits only a moderate ML and BF2dbmOMe shows no detectable ML, all examined under identical conditions.These results confirm that the extent of ML in crystalline organic solid-state fluorophore materials can be correlated positively with the extent of plasticity (low recovery).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata , Mohanpur Campus, Mohanpur 741252, India.

ABSTRACT
The structure and mechanical properties of crystalline materials of three boron difluoride dibenzoylmethane (BF2dbm) derivatives were investigated to examine the correlation, if any, among mechanochromic luminescence (ML) behaviour, solid-state structure, and the mechanical behaviour of single crystals. Qualitative mechanical deformation tests show that the crystals of BF2dbm( (t) Bu)2 can be bent permanently, whereas those of BF2dbm(OMe)2 exhibit an inhomogeneous shearing mode of deformation, and finally BF2dbmOMe crystals are brittle. Quantitative mechanical analysis by nano-indentation on the major facets of the crystals shows that BF2dbm( (t) Bu)2 is soft and compliant with low values of elastic modulus, E, and hardness, H, confirming its superior suceptibility for plastic deformation, which is attributed to the presence of a multitude of slip systems in the crystal structure. In contrast, both BF2dbm(OMe)2 and BF2dbmOMe are considerably stiffer and harder with comparable E and H, which are rationalized through analysis of the structural attributes such as the intermolecular interactions, slip systems and their relative orientation with respect to the indentation direction. As expected from the qualitative mechanical behaviour, prominent ML was observed in BF2dbm( (t) Bu)2, whereas BF2dbm(OMe)2 exhibits only a moderate ML and BF2dbmOMe shows no detectable ML, all examined under identical conditions. These results confirm that the extent of ML in crystalline organic solid-state fluorophore materials can be correlated positively with the extent of plasticity (low recovery). In turn, they offer opportunities to design new and improved efficient ML materials using crystal engineering principles.

No MeSH data available.


Related in: MedlinePlus

Crystal packing of BF2dbm(tBu)2. (a) Schematic diagram of the habit planes or face indices. (b) Distinct faces (major and side faces) of the original crystal and the bent crystal to visualize the bending face. (c) Showing the indentation direction and representation of slip planes formed via hydrophobic tert-butyl groups in BF2dbm(tBu)2 crystal packing. (d) Head-to-tail interaction of molecules via C—H⋯(BF2O2), which are further linked via C—H⋯F interactions to form two-dimensional sheets.
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fig2: Crystal packing of BF2dbm(tBu)2. (a) Schematic diagram of the habit planes or face indices. (b) Distinct faces (major and side faces) of the original crystal and the bent crystal to visualize the bending face. (c) Showing the indentation direction and representation of slip planes formed via hydrophobic tert-butyl groups in BF2dbm(tBu)2 crystal packing. (d) Head-to-tail interaction of molecules via C—H⋯(BF2O2), which are further linked via C—H⋯F interactions to form two-dimensional sheets.

Mentions: BF2dbm(tBu)2 crystallizes in the centrosymmetric monoclinic space group C2/c, with half the molecule in an asymmetric unit (Fig. S1(i), for clarity the full molecule has been shown). Since there are no conventional hydrogen-bonding functional groups, the molecular packing is dominated mainly by weak C—H⋯F interactions. Plenty of examples are available in the literature on the utilization of C—H⋯O and C—H⋯F intermolecular interactions for crystal engineering (Hathwar et al., 2011 ▸; Thalladi et al., 1995 ▸; Schönleber et al., 2014 ▸; Thakur et al., 2010 ▸). Thalladi et al. suggested that C—H⋯F interactions can also be as important as C—H⋯O and C—H⋯N hydrogen bonds for stabilizing the specific crystal structures (Thalladi et al., 1998 ▸; Dunitz & Schweizer, 2006 ▸; Chopra & Row, 2011 ▸). In the present case, the bifurcated C—H⋯F (d/Å, θ/°; 2.56 Å, 167.36°) and C—H⋯B (3.058 Å, 160.76°) interactions between the phenyl and BF2O2 groups connect molecules along the b-axis in a head-to-tail fashion (Fig. 2 ▸d) (Alemany et al., 2014 ▸), which are further linked along the c-axis via an additional C—H⋯F (2.46 Å, 135.98°) interaction to form thick two-dimensional sheets as shown in Fig. 2 ▸(e). The two-dimensional sheets pack together via the close packing of hydrophobic tBu groups resulting in slip planes or weak interaction planes parallel to (100) in the crystal packing (Fig. 2 ▸c). The slip planes exist orthogonal to comparatively strong C—H⋯F interactions. Therefore, the overall crystal packing is anisotropic and hence promotes plasticity in the crystals (Reddy, Kirchner et al., 2006 ▸; Reddy, Padmanabhan et al., 2006 ▸; Ghosh & Reddy, 2012 ▸; Reddy et al., 2010 ▸; Sun & Hou, 2008 ▸; Feng & Grant, 2006 ▸; Reddy et al., 2005 ▸; Panda et al., 2015 ▸).


Structure-mechanical property correlations in mechanochromic luminescent crystals of boron difluoride dibenzoylmethane derivatives.

Krishna GR, Devarapalli R, Prusty R, Liu T, Fraser CL, Ramamurty U, Reddy CM - IUCrJ (2015)

Crystal packing of BF2dbm(tBu)2. (a) Schematic diagram of the habit planes or face indices. (b) Distinct faces (major and side faces) of the original crystal and the bent crystal to visualize the bending face. (c) Showing the indentation direction and representation of slip planes formed via hydrophobic tert-butyl groups in BF2dbm(tBu)2 crystal packing. (d) Head-to-tail interaction of molecules via C—H⋯(BF2O2), which are further linked via C—H⋯F interactions to form two-dimensional sheets.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4645105&req=5

fig2: Crystal packing of BF2dbm(tBu)2. (a) Schematic diagram of the habit planes or face indices. (b) Distinct faces (major and side faces) of the original crystal and the bent crystal to visualize the bending face. (c) Showing the indentation direction and representation of slip planes formed via hydrophobic tert-butyl groups in BF2dbm(tBu)2 crystal packing. (d) Head-to-tail interaction of molecules via C—H⋯(BF2O2), which are further linked via C—H⋯F interactions to form two-dimensional sheets.
Mentions: BF2dbm(tBu)2 crystallizes in the centrosymmetric monoclinic space group C2/c, with half the molecule in an asymmetric unit (Fig. S1(i), for clarity the full molecule has been shown). Since there are no conventional hydrogen-bonding functional groups, the molecular packing is dominated mainly by weak C—H⋯F interactions. Plenty of examples are available in the literature on the utilization of C—H⋯O and C—H⋯F intermolecular interactions for crystal engineering (Hathwar et al., 2011 ▸; Thalladi et al., 1995 ▸; Schönleber et al., 2014 ▸; Thakur et al., 2010 ▸). Thalladi et al. suggested that C—H⋯F interactions can also be as important as C—H⋯O and C—H⋯N hydrogen bonds for stabilizing the specific crystal structures (Thalladi et al., 1998 ▸; Dunitz & Schweizer, 2006 ▸; Chopra & Row, 2011 ▸). In the present case, the bifurcated C—H⋯F (d/Å, θ/°; 2.56 Å, 167.36°) and C—H⋯B (3.058 Å, 160.76°) interactions between the phenyl and BF2O2 groups connect molecules along the b-axis in a head-to-tail fashion (Fig. 2 ▸d) (Alemany et al., 2014 ▸), which are further linked along the c-axis via an additional C—H⋯F (2.46 Å, 135.98°) interaction to form thick two-dimensional sheets as shown in Fig. 2 ▸(e). The two-dimensional sheets pack together via the close packing of hydrophobic tBu groups resulting in slip planes or weak interaction planes parallel to (100) in the crystal packing (Fig. 2 ▸c). The slip planes exist orthogonal to comparatively strong C—H⋯F interactions. Therefore, the overall crystal packing is anisotropic and hence promotes plasticity in the crystals (Reddy, Kirchner et al., 2006 ▸; Reddy, Padmanabhan et al., 2006 ▸; Ghosh & Reddy, 2012 ▸; Reddy et al., 2010 ▸; Sun & Hou, 2008 ▸; Feng & Grant, 2006 ▸; Reddy et al., 2005 ▸; Panda et al., 2015 ▸).

Bottom Line: In contrast, both BF2dbm(OMe)2 and BF2dbmOMe are considerably stiffer and harder with comparable E and H, which are rationalized through analysis of the structural attributes such as the intermolecular interactions, slip systems and their relative orientation with respect to the indentation direction.As expected from the qualitative mechanical behaviour, prominent ML was observed in BF2dbm( (t) Bu)2, whereas BF2dbm(OMe)2 exhibits only a moderate ML and BF2dbmOMe shows no detectable ML, all examined under identical conditions.These results confirm that the extent of ML in crystalline organic solid-state fluorophore materials can be correlated positively with the extent of plasticity (low recovery).

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata , Mohanpur Campus, Mohanpur 741252, India.

ABSTRACT
The structure and mechanical properties of crystalline materials of three boron difluoride dibenzoylmethane (BF2dbm) derivatives were investigated to examine the correlation, if any, among mechanochromic luminescence (ML) behaviour, solid-state structure, and the mechanical behaviour of single crystals. Qualitative mechanical deformation tests show that the crystals of BF2dbm( (t) Bu)2 can be bent permanently, whereas those of BF2dbm(OMe)2 exhibit an inhomogeneous shearing mode of deformation, and finally BF2dbmOMe crystals are brittle. Quantitative mechanical analysis by nano-indentation on the major facets of the crystals shows that BF2dbm( (t) Bu)2 is soft and compliant with low values of elastic modulus, E, and hardness, H, confirming its superior suceptibility for plastic deformation, which is attributed to the presence of a multitude of slip systems in the crystal structure. In contrast, both BF2dbm(OMe)2 and BF2dbmOMe are considerably stiffer and harder with comparable E and H, which are rationalized through analysis of the structural attributes such as the intermolecular interactions, slip systems and their relative orientation with respect to the indentation direction. As expected from the qualitative mechanical behaviour, prominent ML was observed in BF2dbm( (t) Bu)2, whereas BF2dbm(OMe)2 exhibits only a moderate ML and BF2dbmOMe shows no detectable ML, all examined under identical conditions. These results confirm that the extent of ML in crystalline organic solid-state fluorophore materials can be correlated positively with the extent of plasticity (low recovery). In turn, they offer opportunities to design new and improved efficient ML materials using crystal engineering principles.

No MeSH data available.


Related in: MedlinePlus