01264nas a2200157 4500008004100000245010600041210006900147260000800216300001400224490000700238520066800245100002000913700002200933700002600955856012500981 2024 eng d00aStructural basis for a two-dimensional flexible pharmaceutical solvate crystal: indomethacin methanol0 aStructural basis for a twodimensional flexible pharmaceutical so cOCT a5694-56980 v263 a

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.

1 aBhowmik, Aritra1 aBamane, Sanjivani1 aMishra, Manish, Kumar uhttps://library.ncl.res.in/content/structural-basis-two-dimensional-flexible-pharmaceutical-solvate-crystal-indomethacin02314nas a2200181 4500008004100000022001400041245010700055210006900162260000900231300001400240490000700254520165900261100002001920700002201940700002601962700002601988856011802014 2025 eng d a1528-748300aCaffeine vs. theophylline cocrystals: insights into structure-mechanical behavior and piezoelectricity0 aCaffeine vs theophylline cocrystals insights into structuremecha cJUN  a5007-50210 v253 a

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.

1 aBhowmik, Aritra1 aBamane, Sanjivani1 aSaxena, Ashish, Kumar1 aMishra, Manish, Kumar uhttps://library.ncl.res.in/content/caffeine-vs-theophylline-cocrystals-insights-structure-mechanical-behavior-and02285nas a2200181 4500008004100000022001400041245008600055210006900141260000800210300001600218490000700234520166200241100001501903700002001918700002601938700002101964856011801985 2025 eng d a1528-748300aIntegrating thermal actuation and acidochromism in schiff base molecular crystals0 aIntegrating thermal actuation and acidochromism in schiff base m cDEC a10527-105400 v253 a

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.

1 aNag, Sayak1 aBhowmik, Aritra1 aMishra, Manish, Kumar1 aGhosh, Soumyajit uhttps://library.ncl.res.in/content/integrating-thermal-actuation-and-acidochromism-schiff-base-molecular-crystals02198nas a2200181 4500008004100000022001400041245011000055210006900165260000800234300001400242490000700256520153600263100001901799700002001818700002601838700002101864856013101885 2025 eng d a1528-748300aMechanical flexibility, photosalience, and acidochromism of benzylidene indanone-based molecular crystals0 aMechanical flexibility photosalience and acidochromism of benzyl cJUN a4481-44930 v253 a

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.

1 aAhamed, Riyaaz1 aBhowmik, Aritra1 aMishra, Manish, Kumar1 aGhosh, Soumyajit uhttps://library.ncl.res.in/content/mechanical-flexibility-photosalience-and-acidochromism-benzylidene-indanone-based-molecular01239nas a2200181 4500008004100000022001400041245009000055210006900145260000800214300001600222490000700238520060400245100002200849700002000871700002600891700002100917856011900938 2025 eng d a1359-734500aWater-driven modulation of multiresponsive properties in acylhydrazone-based crystals0 aWaterdriven modulation of multiresponsive properties in acylhydr cAUG a12139-121420 v613 a

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's potential for smart actuators and photoswitchable devices.

1 aManoharan, Deepak1 aBhowmik, Aritra1 aMishra, Manish, Kumar1 aGhosh, Soumyajit uhttps://library.ncl.res.in/content/water-driven-modulation-multiresponsive-properties-acylhydrazone-based-crystals01116nas a2200181 4500008004100000022001400041245008800055210006900143260000800212300001400220490000700234520047800241100003000719700002000749700002600769700002100795856011800816 2026 eng d a1359-734500aHelically twistable cyanoacrylate crystal with simultaneous photomechanical bending0 aHelically twistable cyanoacrylate crystal with simultaneous phot cMAY a8661-86640 v623 a

A cyanoacrylate derivative crystal exhibits an unusual combination of one-dimensional elasticity, plasticity, and reversible hand-held twisting. Twisting induces a reversible single crystal to polycrystal transition. It also displays photobending via a cycloaddition reaction under 365 nm irradiation and thermally recovers its original state, retaining functionality in the twisted state, indicating potential applications in soft robotics and smart actuators.

1 aParthasarathy, Thiyagaraj1 aBhowmik, Aritra1 aMishra, Manish, Kumar1 aGhosh, Soumyajit uhttps://library.ncl.res.in/content/helically-twistable-cyanoacrylate-crystal-simultaneous-photomechanical-bending01270nas a2200193 4500008004100000022001400041245010100055210006900156260000900225300001200234490000700246520057500253100003000828700002000858700002700878700002600905700002100931856012400952 2026 eng d a1359-734500aReversible twisting-induced crystalline-polycrystalline transformation in cyanoacrylate crystals0 aReversible twistinginduced crystallinepolycrystalline transforma cJAN  a264-2670 v623 a

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.

1 aParthasarathy, Thiyagaraj1 aBhowmik, Aritra1 aBhattacharya, Biswajit1 aMishra, Manish, Kumar1 aGhosh, Soumyajit uhttps://library.ncl.res.in/content/reversible-twisting-induced-crystalline-polycrystalline-transformation-cyanoacrylate