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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

Representative P–h curves obtained from the molecular crystals of BF2dbm(tBu)2 (black line), BF2dbm(OMe)2 (blue line) and BF2dbmOMe (red line).
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fig5: Representative P–h curves obtained from the molecular crystals of BF2dbm(tBu)2 (black line), BF2dbm(OMe)2 (blue line) and BF2dbmOMe (red line).

Mentions: Quantification of mechanical properties by nanoindentation (NI) experiments: Recent work has successfully demonstrated that the NI technique can be utilized to quantify the mechanical properties of molecular crystals, and in turn not only establish the structure–property correlations, but also use such knowledge for designing organic solids with specific targeted properties. The major faces of the crystals of BF2dbm(tBu)2, BF2dbm(OMe)2 and BF2dbmOMe were all indented in load-control mode with a Berkovich tip, and (un)loading rates of 0.2 mN s−1, peak load, Pmax, of 1 mN, and Pmax hold time of 2 s. Representative load, P, versus depth, h, curves are displayed in Fig. 5 ▸, which reveal the following significant differences in the mechanical responses of the three compounds examined.


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)

Representative P–h curves obtained from the molecular crystals of BF2dbm(tBu)2 (black line), BF2dbm(OMe)2 (blue line) and BF2dbmOMe (red line).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig5: Representative P–h curves obtained from the molecular crystals of BF2dbm(tBu)2 (black line), BF2dbm(OMe)2 (blue line) and BF2dbmOMe (red line).
Mentions: Quantification of mechanical properties by nanoindentation (NI) experiments: Recent work has successfully demonstrated that the NI technique can be utilized to quantify the mechanical properties of molecular crystals, and in turn not only establish the structure–property correlations, but also use such knowledge for designing organic solids with specific targeted properties. The major faces of the crystals of BF2dbm(tBu)2, BF2dbm(OMe)2 and BF2dbmOMe were all indented in load-control mode with a Berkovich tip, and (un)loading rates of 0.2 mN s−1, peak load, Pmax, of 1 mN, and Pmax hold time of 2 s. Representative load, P, versus depth, h, curves are displayed in Fig. 5 ▸, which reveal the following significant differences in the mechanical responses of the three compounds examined.

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