@article {49655, title = {Simultaneously mechanically flexible, photobending, and acidochromic cyanostilbene molecular crystals}, journal = {Crystal Growth \& Design}, volume = {25}, year = {2024}, month = {DEC}, pages = {309-318}, type = {Article}, abstract = {

Molecular crystals that respond to multiple stimuli are gaining significant attention for their potential in smart materials like actuators and sensors. However, imparting multiple stimuli-responsive properties to a single crystal remains a major challenge. Herein, we report two cyanostilbene derivative-based crystals 1 and 2, with various responses to stimuli such as mechanical stress, light, acid vapors, etc. Both crystals 1 and 2 demonstrated mechanical flexibility and reversible acidochromism. Additionally, crystal 1 also exhibited light-induced photobending, which is ascribed to Z to E photoisomerization. Detailed structure-property correlation was established to unravel distinct mechanical responses. The development of these multitasking crystals may find applications in multitasking actuators, anticounterfeiting materials, and more.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.4c01341}, author = {Parthasarathy, Thiyagaraj and Mishra, Manish Kumar and Bhattacharya, Biswajit and Emmerling, Franziska and Ghosh, Soumyajit} } @article {49297, title = {Structural basis for a two-dimensional flexible pharmaceutical solvate crystal: indomethacin methanol}, journal = {CrystEngComm}, volume = {26}, year = {2024}, month = {OCT}, pages = {5694-5698}, type = {Article}, abstract = {

We report the first two-dimensionally (2D) elastically bendable and twistable pharmaceutical-solvate crystal, indomethacin methanol. Its flexibility is due to interlocked packing and a structural buffer acting like isotropic interactions. For the first time, we utilized Raman spectroscopy on the two elastic faces of a bent crystal region, revealing the inhomogeneous molecular distribution in the crystal structure during bending and validating the mechanistic model of the 2D elastic crystal. We present the first 2D elastic pharmaceutical-solvate crystal and utilized Raman spectroscopy to reveal inhomogeneous lattice distribution during bending.

}, doi = {10.1039/d4ce00920g}, author = {Bhowmik, Aritra and Bamane, Sanjivani and Mishra, Manish Kumar} } @article {49390, title = {Template-asisted visible light-induced [2+2] photodimerization in a pseudopolymorphic binary solid: topotactic transformation vs photoinduced crystal melting}, journal = {CRYSTAL GROWTH \& DESIGN}, volume = {24}, year = {2024}, month = {MAY }, pages = {5193-5199}, type = {Journal Article}, keywords = {CATION-PI INTERACTIONS, SINGLE-CRYSTAL, STATE PHOTODIMERIZATION, Supramolecular}, issn = {1528-7483}, doi = {10.1021/acs.cgd.4c00426}, author = {Ahsan, Mollah Rohan and Varma, Harshit and Mishra, Manish Kumar and Mukherjee, Arijit} } @article {49911, title = {Caffeine vs. theophylline cocrystals: insights into structure-mechanical behavior and piezoelectricity}, journal = {Crystal Growth \& Design}, volume = {25}, year = {2025}, month = {JUN }, pages = {5007-5021}, type = {Article}, abstract = {

Cocrystallization offers a versatile approach to modulate the physicochemical including mechanical properties of active pharmaceutical ingredients (APIs). In this study, we employ crystal engineering principles to design cocrystals of two structurally similar methylxanthine compounds-caffeine (CAF) and theophylline (THP)-with 3,5-dinitrosalicylic acid (DNSA) and 3,5-dinitrobenzoic acid (DNBA) as coformers. The resulting cocrystals and cocrystal polymorphs displayed diverse architectures-2D layers, corrugated sheets, and 3D interlocked structures-showing distinct deformation characteristics. Particular attention was given to the mechanical shearing of the layered structure cocrystals THP-DNBA and CAF-DNBA-I, which are critical for pharmaceutical manufacturing processes such as tablet compaction. The sheared fragmented crystal of THP-DNBA also shows plastic bending deformation. On the other hand, the CAF-DNSA, CAF-DNBA-II, and THP-DNSA cocrystals are brittle due to the absence of a flat layer structure. Our findings reveal that structural features such as flat molecular geometry, pi-stacking, and weak interlayer interactions play crucial roles in promoting plastic deformation via shearing and plastic bending. Nanoindentation studies have been performed on the major faces of all the cocrystals to quantify their mechanical properties. Notably, the CAF-DNBA-I cocrystal also exhibited piezoelectric properties. This work provides valuable insights into the structure-mechanical property relationship in pharmaceutical cocrystals and underscores the potential of cocrystallization in addressing formulation-related challenges.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.5c00491}, author = {Bhowmik, Aritra and Bamane, Sanjivani and Saxena, Ashish Kumar and Mishra, Manish Kumar} } @article {49922, title = {Integrating thermal actuation and acidochromism in schiff base molecular crystals}, journal = {Crystal Growth \& Design}, volume = {25}, year = {2025}, month = {DEC}, pages = {10527-10540}, type = {Article}, abstract = {

Crystalline materials capable of responding to multiple external stimuli have garnered considerable attention in recent years due to their promising potential for various applications in smart materials, sensing, and actuation. In this paper, we report the synthesis and characterization of two developed linker-based Schiff base molecular crystals, designated as 1 and 2, both of which exhibit two distinct reversible stimuli-responsive behaviors: (i) a thermal expansion-contraction response during repeated heating and cooling cycles and (ii) a reversible acidochromic color change upon sequential exposure to acidic and basic vapors. Importantly, these two reversible responses are governed by entirely distinct underlying processes. The thermal expansion-contraction behavior is driven by a martensitic phase transition, from a low-temperature phase to a high-temperature phase, which involves rapid and reversible lattice displacive rearrangements. In contrast, the acidochromic color change arises from a disruption in the electronic conjugation within the molecular framework, where the system undergoes a transformation from an A-pi-D-pi-A (acceptor-pi-donor-pi-acceptor) configuration to an A-pi-A-pi-A (acceptor-pi-acceptor-pi-acceptor) configuration upon protonation, manifested by a distinct shift in optical absorption properties. The unique combination of these two reversible phenomena-thermal expansion-contraction and acidochromic responses-within a single material system offers significant potential for advanced applications, particularly in the development of acid-sensitive sensors and thermally responsive microactuators.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.5c01283}, author = {Nag, Sayak and Bhowmik, Aritra and Mishra, Manish Kumar and Ghosh, Soumyajit} } @article {49717, title = {Mechanical flexibility, photosalience, and acidochromism of benzylidene indanone-based molecular crystals}, journal = {Crystal Growth \& Design}, volume = {25}, year = {2025}, month = {JUN}, pages = {4481-4493}, type = {Article}, abstract = {

Molecular crystals that respond to multiple external stimuli are of great interest in smart, responsive materials in various fields. However, the integration of multiple responsive properties within the same crystal still remains a significant challenge for materials scientists due to the complex structural and electronic interactions. Previous studies on benzylidene indanone-based molecular crystals have shown only mechanical plasticity; however, we design crystals to elicit diverse responses to external stimuli, including mechanical stress, light, and acid vapor. Herein, we report two benzylidene indanone derivative-based crystals 1 and 2. Crystal 1 is mechanically brittle and exhibits light-induced photosalient splitting and jumping, attributed to [2 + 2] cycloaddition facilitated by the presence of a vinyl moiety. On the other hand, crystal 2 demonstrates anisotropic mechanical flexibility, exhibiting elasticity on one face and plasticity on alternate faces. Furthermore, crystals 1 and 2 both display reversible acidochromism in response to acid vapor. A detailed structure-property correlation has been established to elucidate the distinct mechanical responses of these molecular crystals. The development of such multistimuli-responsive smart materials holds significant potential for applications in flexible acid sensors, multifunctional responsive smart devices, and actuators, paving the way for advanced smart or intelligent molecular materials with tunable mechanical and optical properties.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.5c00389}, author = {Ahamed, Riyaaz and Bhowmik, Aritra and Mishra, Manish Kumar and Ghosh, Soumyajit} } @article {49708, title = {Photo-induced cracking in a Bi-component molecular solid: capturing structural intermediates}, journal = {Chemistry-An Asian Journal}, volume = {20}, year = {2025}, month = {MAY}, type = {Article}, abstract = {

A photo-responsive bi-component solid is designed based on robust large synthons. The study not only provides a template-based approach for a system that was difficult to photo-dimerize, but the designed solid also leads to photo-induced cracking upon photodimerization. The delicate structural design helps in capturing the structural intermediates, which reveals a possible reorientation of the photodimer within the crystal to maintain structural integrity.

}, keywords = {bi-component solid, crystal engineering, photoinduced cracking, single-crystal-to-single crystal transformation, [2+2] photodimerization}, issn = {1861-4728}, doi = {10.1002/asia.202401518}, author = {Ahsan, Mollah Rohan and Mishra, Manish Kumar and Mukherjee, Arijit} } @article {49920, title = {Water-driven modulation of multiresponsive properties in acylhydrazone-based crystals}, journal = {Chemical Communications}, volume = {61}, year = {2025}, month = {AUG}, pages = {12139-12142}, type = {Article}, abstract = {

A pyrene-substituted acylhydrazone (PyAc) crystal undergoes a water-driven transition from elasticity to thermoplastic bending. The hydrated crystal remains two-dimensional (2D) elastic until heating, after which it becomes brittle and bent upon dehydration. While the hydrated crystal is non-photoresponsive, the anhydrous form exhibits photomechanical bending due to favorable E-Z photoisomerization. These distinct properties, governed by solvent channels, molecular packing, and non-covalent interactions, demonstrate PyAc{\textquoteright}s potential for smart actuators and photoswitchable devices.

}, issn = {1359-7345}, doi = {10.1039/d5cc01375e}, author = {Manoharan, Deepak and Bhowmik, Aritra and Mishra, Manish Kumar and Ghosh, Soumyajit} } @article {49943, title = {Reversible twisting-induced crystalline-polycrystalline transformation in cyanoacrylate crystals}, journal = {Chemical Communications}, volume = {62}, year = {2026}, month = {JAN }, pages = {264-267}, type = {Article}, abstract = {

We report cyanoacrylate-based organic crystalline materials that exhibit reversible hand-induced helical twisting through the combined action of 1D elasticity and 2D plasticity. These crystals twist and untwist without lattice damage, retaining their elastic integrity through pi slip-stacking and Cl \& ctdot;Cl, C-H \& ctdot;Cl, and Me \& ctdot;Me interactions. Their unique integration of elastic recovery, plastic bending, and reversible twisting highlights their potential as mechanically adaptive materials for flexible and responsive devices.

}, issn = {1359-7345}, doi = {10.1039/d5cc05852j}, author = {Parthasarathy, Thiyagaraj and Bhowmik, Aritra and Bhattacharya, Biswajit and Mishra, Manish Kumar and Ghosh, Soumyajit} }