Mechanistic Insights into Mechanically Flexible Molecular Crystals: from Design to Synthesis

• Applicant: Dr. Biswajit Bhattacharya
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Synthesis and Properties of Functional Materials
• Term: from 2020 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 450137475

• Final Report Year: 2025

Final Report Abstract

This project elucidated the molecular mechanisms underlying mechanical flexibility in molecular crystals, a phenomenon with significant potential for advanced technologies. Flexible crystals, including organic compounds and coordination polymers (CPs), were synthesized using weak intermolecular interactions like van der Waals forces, halogen bonding, and π-π stacking. The structural evolution during bending was studied using advanced techniques, including synchrotron-based micro-focus XRD, micro-Raman scattering, FTIR spectroscopy, and nanoindentation, revealing critical mechano-structural relationships. Elastic and elastoplastic bending properties were investigated, and the flexibility of CPs was tunable by modifying their covalent backbones without altering crystal structures. Predictive models for designing flexible crystals were proposed, reducing reliance on empirical methods. Additionally, the synthesized crystals demonstrated waveguiding properties, showcasing their potential in flexible optical devices and photonic technologies. Through the successful execution of this project, the library of flexible molecular crystals has been expanded, and robust methodologies for their synthesis and characterization have been established. These advancements represent a significant step toward the integration of these materials into next-generation technologies, including smart optoelectronics, biomedical devices, pharmaceuticals, and energy-harvesting devices based on piezoelectric flexible crystals.

Publications

• Tuning the mechanical flexibility of organic molecular crystals by polymorphism for flexible optical waveguides. CrystEngComm, 23(34), 5815-5825.
  Feiler, Torvid; Bhattacharya, Biswajit; Michalchuk, Adam A. L.; Rhim, Seon-Young; Schröder, Vincent; List-Kratochvil, Emil & Emmerling, Franziska
  
• Adaptable Optical Microwaveguides From Mechanically Flexible Crystalline Materials. Chemistry – A European Journal, 28(40).
  Chinnasamy, Ragaverthini; Ravi, Jada; Vinay, Pradeep Vuppu; Manoharan, Deepak; Emmerling, Franziska; Bhattacharya, Biswajit; Ghosh, Soumyajit & Chandrasekar, Rajadurai
  
• Designing Dual Mechanical Response in Molecular Crystals through Cocrystallization. Crystal Growth & Design, 22(12), 6838-6843.
  Lakshmipathi, Madhumathi; Dey, Somnath; Emmerling, Franziska; Bhattacharya, Biswajit; Michalchuk, Adam A. L. & Ghosh, Soumyajit
  
• Different mechanical responses of dimorphic forms of Anthracene Schiff base crystal. Journal of Molecular Structure, 1252, 132182.
  Lakshmipathi, Madhumathi; Tothadi, Srinu; Emmerling, Franziska; Bhattacharya, Biswajit & Ghosh, Soumyajit
  
• Mechanically flexible crystals of styryl quinoline derivatives. Journal of Molecular Structure, 1265, 133293.
  Thekkeppat, Nipun P.; Bhattacharya, Biswajit; Tothadi, Srinu & Ghosh, Soumyajit
  
• Plastically Bendable Organic Crystals for Monolithic and Hybrid Micro‐Optical Circuits. Advanced Optical Materials, 11(13).
  Ravi, Jada; Feiler, Torvid; Mondal, Amit; Michalchuk, Adam A. L.; Reddy, C. Malla; Bhattacharya, Biswajit; Emmerling, Franziska & Chandrasekar, Rajadurai
  
• Structure-mechanical property correlation of a series of 4-(1-Napthylvinyl) pyridine based cocrystals. Journal of Molecular Structure, 1268, 133670.
  Lakshmipathi, Madhumathi; Emmerling, Franziska; Bhattacharya, Biswajit & Ghosh, Soumyajit
  
• An atomistic mechanism for elasto-plastic bending in molecular crystals. Chemical Science, 14(13), 3441-3450.
  Bhattacharya, Biswajit; Michalchuk, Adam A. L.; Silbernagl, Dorothee; Yasuda, Nobuhiro; Feiler, Torvid; Sturm, Heinz & Emmerling, Franziska
  
• Designing the Mechanical Plasticity of Benzylidene Indanones Based Molecular Crystals by Crystal Engineering. Crystal Growth & Design, 23(2), 657-661.
  Manoharan, Deepak; S., N. Megha; Kiran, Mangalampalli S. R. N.; Emmerling, Franziska; Bhattacharya, Biswajit & Ghosh, Soumyajit
  
• Linker size dependent mechanical properties of di-imine based molecular crystals. CrystEngComm, 25(46), 6416-6423.
  Manoharan, Deepak; Ahmad, Shamim; Tothadi, Srinu; Emmerling, Franziska; Bhattacharya, Biswajit & Ghosh, Soumyajit
  
• Mechanistic Investigation of an Elastically Flexible Organic Crystal. Crystal Growth & Design, 23(9), 6244-6249.
  Feiler, Torvid; Yasuda, Nobuhiro; Michalchuk, Adam A. L.; Emmerling, Franziska & Bhattacharya, Biswajit
  
• Stepwise Tuning the Mechanical Flexibility of 1D Coordination Polymer Single Crystals. American Chemical Society (ACS).
  Bhattacharya, Biswajit; Michalchuk, Adam; Silbernagel, Dorothee; Sturm, Heinz & Emmerling, Franziska
  
• Stress and light sensitive dual-mechanical property of acylhydrazone crystal. CrystEngComm, 25(21), 3237-3244.
  Manoharan, Deepak; Ahmad, Shamim; Emmerling, Franziska; Bhattacharya, Biswajit & Ghosh, Soumyajit
  
• Design of mechanically flexible photoresponsive cyanostilbene molecular crystals. CrystEngComm, 26(34), 4634-4642.
  Parthasarathy, Thiyagaraj; Bhattacharya, Biswajit; Emmerling, Franziska & Ghosh, Soumyajit
  
• Distinct photomechanical responses of two new 1,3-dimethylbarbituric acid derivative crystals. CrystEngComm, 26(22), 2871-2882.
  Nag, Sayak; Emmerling, Franziska; Tothadi, Srinu; Bhattacharya, Biswajit & Ghosh, Soumyajit
  
• Elasto-plastic behaviour with reversible thermosalient expansion in acrylonitrile-based organic crystals. Journal of Materials Chemistry C, 12(7), 2515-2525.
  Manoharan, Deepak; Ranjan, Subham; Emmerling, Franziska; Bhattacharya, Biswajit; Takamizawa, Satoshi & Ghosh, Soumyajit
  
• Simultaneously Mechanically Flexible, Photobending, and Acidochromic Cyanostilbene Molecular Crystals. Crystal Growth & Design, 25(2), 309-318.
  Parthasarathy, Thiyagaraj; Mishra, Manish Kumar; Bhattacharya, Biswajit; Emmerling, Franziska & Ghosh, Soumyajit
  
• Synergistic Catalytic Sites in High‐Entropy Metal Hydroxide Organic Framework for Oxygen Evolution Reaction. Advanced Materials, 36(52).
  Roy, Arkendu; Kumar, Sourabh; Guilherme, Buzanich Ana; Prinz, Carsten; Götz, Emilia; Retzmann, Anika; Hickel, Tilmann; Bhattacharya, Biswajit & Emmerling, Franziska
  
• Mechanochemical ZIF-9 formation: in situ analysis and photocatalytic enhancement evaluation. RSC Mechanochemistry, 2(1), 116-126.
  Rodríguez-Sánchez, Noelia; Prinz, Carsten; Bienert, Ralf; Ballesteros, Menta; Ruiz, Salvador A. Rabdel; Bhattacharya, Biswajit & Emmerling, Franziska