@article { ISI:000303366000001, title = {Polymorphs, salts, and cocrystals: what{\textquoteright}s in a name?}, journal = {Crystal Growth \& Design}, volume = {12}, number = {5}, year = {2012}, month = {MAY}, pages = {2147-2152}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The December 2011 release of a draft United States Food and Drug Administration (FDA) guidance concerning regulatory classification of pharmaceutical cocrystals of active pharmaceutical ingredients (APIs) addressed two matters of topical interest to the crystal engineering and pharmaceutical science communities: (1) a proposed definition of cocrystals; (2) a proposed classification of pharmaceutical cocrystals as dissociable {\textquoteleft}{\textquoteleft}API-excipient{\textquoteright}{\textquoteright} molecular complexes. The Indo U.S. Bilateral Meeting sponsored by the Indo-U.S. Science and Technology Forum titled The Evolving Role of Solid State Chemistry in Pharmaceutical Science was held in Manesar near Delhi, India, from February 2-4, 2012. A session of the meeting was devoted to discussion of the FDA guidance draft. The debate generated strong consensus on the need to define cocrystals more broadly and to classify them like salts. It was also concluded that the diversity of API crystal forms makes it difficult to classify solid forms into three categories that are mutually exclusive. This perspective summarizes the discussion in the Indo-U.S. Bilateral Meeting and includes contributions from researchers who were not participants in the meeting.

}, issn = {1528-7483}, doi = {10.1021/cg3002948}, author = {Aitipamula, Srinivasulu and Banerjee, Rahul and Bansal, Arvind K. and Biradha, Kumar and Cheney, Miranda L. and Choudhury, Angshuman Roy and Desiraju, Gautam R. and Dikundwar, Amol G. and Dubey, Ritesh and Duggirala, Nagakiran and Ghogale, Preetam P. and Ghosh, Soumyajit and Goswami, Pramod Kumar and Goud, N. Rajesh and Jetti, Ram R. K. R. and Karpinski, Piotr and Kaushik, Poonam and Kumar, Dinesh and Kumar, Vineet and Moulton, Brian and Mukherjee, Arijit and Mukherjee, Gargi and Myerson, Allan S. and Puri, Vibha and Ramanan, Arunachalam and Rajamannar, T. and Reddy, C. Malla and Rodriguez-Hornedo, Nair and Rogers, Robin D. and Row, T. N. Guru and Sanphui, Palash and Shan, Ning and Shete, Ganesh and Singh, Amit and Sun, Changquan C. and Swift, Jennifer A. and Thaimattam, Ram and Thakur, Tejender S. and Thaper, Rajesh Kumar and Thomas, Sajesh P. and Tothadi, Srinu and Vangala, Venu R. and Variankaval, Narayan and Vishweshwar, Peddy and Weyna, David R. and Zaworotko, Michael J.} } @article { ISI:000306942300059, title = {Polymorphs, salts and cocrystals: what{\textquoteright}s in a name? (vol 12, pg 2147, 2012)}, journal = {Crystal Growth \& Design}, volume = {12}, number = {8}, year = {2012}, month = {AUG}, pages = {4290-4291}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, issn = {1528-7483}, doi = {10.1021/cg300704b}, author = {Aitipamula, Srinivasulu and Banerjee, Rahul and Bansal, Arvind K. and Biradha, Kumar and Cheney, Miranda L. and Choudhury, Angshuman Roy and Desiraju, Gautam R. and Dikundwar, Amol G. and Dubey, Ritesh and Duggirala, Nagakiran and Ghogale, Preetam P. and Ghosh, Soumyajit and Goswami, Pramod Kumar and Goud, N. Rajesh and Jetti, Ram R. K. R. and Karpinski, Piotr and Kaushik, Poonam and Kumar, Dinesh and Kumar, Vineet and Moulton, Brian and Mukherjee, Arijit and Mukherjee, Gargi and Myerson, Allan S. and Puri, Vibha and Ramanan, Arunachalam and Rajamannar, T. and Reddy, C. Malla and Rodriguez-Hornedo, Nair and Rogers, Robin D. and Row, T. N. Guru and Sanphui, Palash and Shan, Ning and Shete, Ganesh and Singh, Amit and Sun, Changquan C. and Swift, Jennifer A. and Thaimattam, Ram and Thakur, Tejender S. and Thaper, Rajesh Kumar and Thomas, Sajesh P. and Tothadi, Srinu and Vangala, Venu R. and Vishweshwar, Peddy and Weyna, David R. and Zaworotko, Michael J.} } @article {46187, title = {Remarkably distinct mechanical flexibility in three structurally similar semiconducting organic crystals studied by nanoindentation and molecular dynamics}, journal = {Chemistry of Materials}, volume = {31}, year = {2019}, month = {FEB}, pages = {1391-1402}, type = {Article}, abstract = {

Distinct macroscopic mechanical responses of the three crystals of naphthalene diimide derivatives, 1Me, 1Et, and 1nPr, studied here are very intriguing because their molecular structures are very similar, with the difference only in the alkyl chain length. Among the three crystals examined, 1Me shows highly plastic bending nature, 1Et shows elastic flexibility, and 1nPr is brittle. A detailed investigation by nanoindentation and molecular dynamics (MD) simulations allowed us to correlate their distinct mechanical responses with the way the weak interactions pack in crystal structures. The elastic modulus (E) of 1Me is nearly an order of magnitude lower than that of 1Et, whereas hardness (H) is less than half. The low values of E and H of 1Me indicate that these crystals are highly compliant and offer a low resistance to plastic flow. As the knowledge of hardness and elastic modulus of molecular crystals alone is insufficient to capture their macroscopic mechanical deformation nature, that is, elastic, brittle, or plastic, we have employed three-point bending tests using the nanoindentation technique. This allowed a quantitative evaluation of flexibility of the three mechanically distinct semiconducting molecular crystals, which is important for designing larger-scale applications; these were complemented with detailed MD simulations. The elastic 1Et crystals showed remarkable flexibility even after 1000 cycles. The results emphasize that the alkyl side chains in functional organic crystals may be exploited for tuning their self-assembly as well as their mechanical properties. Hence, the study has broad implications, for example, in crystal engineering of various flexible, ordered molecular materials.

}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.8b04800}, author = {Devarapalli, Ramesh and Kadambi, Sourabh Bhagwan and Chen, Chun-Teh and Krishna, Gamidi Rama and Kammari, Bal Raju and Buehler, Markus J. and Ramamurty, Upadrasta and Reddy, C. Malla} } @article {48417, title = {Dual nanomechanics in anisotropic porous covalent organic framework janus-type thin films}, journal = {Journal of the American Chemical Society}, volume = {144}, year = {2022}, month = {JAN}, pages = {400-409}, type = {Article}, abstract = {

Empowered by crystalline ordered structures and homogeneous fabrication techniques, covalent organic frameworks (COFs) have been realized with uniform morphologies and isotropic properties. However, such homogeneity often hinders various surface-dependent properties observed in asymmetric nanostructures. The challenge remains to induce heterogeneity in COFs by creating an asymmetric superstructure such as a Janus thin film. In this regard, we propose a versatile yet straightforward interfacial layer-grafting strategy to fabricate free-standing Janus-type COF-graphene thin films. Herein, two-dimensional graphene sheets were utilized as the suitable grafter due to the possibility of noncovalent interactions between the layers. The versatility of the approach was demonstrated by fabricating two distinct Janus-type films, with the COF surface interwoven with nanofibers and nanospheres. The Janus-type films showcase opposing surface morphologies originating from graphene sheets and COF nanofibers or nanospheres, preserving the porosity (552-600 m(2) g(-1)). The unique surface chemistries of the constituent layers further endow the films with orthogonal mechanical properties, as confirmed by the nanoindentation technique. Interestingly, the graphene sheets favor the Janus-type assembly of COF nanofibers over the nanospheres. This is reflected in the better nanomechanical properties of COFfiber-graphene films (E-gra(phene) = 300-1200 MPa; E-COF( )= 15-60 MPa) compared to the COFsphere-graphene films (E-gra(phe)ne = 11-14 MPa; E-CO(F )= 2-5 MPa). These results indicate a direct relationship between the mechanical properties and homo/heterogeneity of Janus-type COF films.

}, issn = {0002-7863}, doi = {10.1021/jacs.1c10263}, author = {Mohata, Shibani and Dey, Kaushik and Bhunia, Surojit and Thomas, Neethu and Gowd, E. Bhoje and Ajithkumar, Thalasseril G. and Reddy, C. Malla and Banerjee, Rahul} } @article {48416, title = {Viscoelastic covalent organic nanotube fabric via macroscopic entanglement}, journal = {Journal of the American Chemical Society}, volume = {144}, year = {2022}, month = {SEP }, pages = {16052-16059}, type = {Article}, abstract = {

Covalent organic nanotubes (CONTs) are one-dimensional porous frameworks constructed from organic building blocks via dynamic covalent chemistry. CONTs are synthesized as insoluble powder that restricts their potential applications. The judicious selection of 2,2{\textquoteright}-bipyridine-5,5{\textquoteright}-dicarbaldehyde and tetraaminotriptycene as building blocks for TAT-BPy CONTs has led to constructing flexible yet robust and self-standing fabric up to 3 mu m thickness. The TAT-BPy CONTs and TAT-BPy CONT fabric have been characterized by solid-state one-dimensional (1D) C-13 CP-MAS, two-dimensional (2D) C-13-H-1 correlation NMR, 2D H-1-H-1 DQ-SQ NMR, and 2D N-14-H-1 correlation NMR spectroscopy. The mechanism of fabric formation has been established by using high-resolution transmission electron microscopy and scanning electron microscopy techniques. The as-synthesized viscoelastic TAT-BPy CONT fabric exhibits high mechanical strength with a reduced modulus (E-r) of 8 (+/- 3) GPa and hardness (H) of 0.6 (+/- 0.3) GPa. Interestingly, the viscoelastic fabric shows time-dependent elastic depth recovery up to 50-70\%.

}, issn = {0002-7863}, doi = {10.1021/jacs.2c06133}, author = {Koner, Kalipada and Das, Susobhan and Mohata, Shibani and Duong, Nghia Tuan and Nishiyama, Yusuke and Kandambeth, Sharath and Karak, Suvendu and Reddy, C. Malla and Banerjee, Rahul} }