Functionalized organic frameworks explored as second order NLO agents

A new class of chiral phthalimides functionalized with aryl piperazines was designed anticipating their strong candidature for crystal engineering and technological applications. Five new phthalimides were synthesized, characterized and subjected to single crystal X-ray diffraction study that directed their non-centrosymmetric structures. Four phthalimides crystallized in P2(1) space group with monoclinic crystal system, however, one was found to possess P2(1)2(1)2(1) space group with orthorhombic system. The supramolecular architectures of phthalimide crystals were analysed by an approach based on consideration of energy of intermolecular interaction. The molecular hyperpolarizability (beta) calculation for all the listed phthalimides indicated their promising candidature for NLO materials. Further, the crystalline form of all phthalimides was evaluated for their second harmonic generation (SHG) response. A significant response of 16.4 mV was measured for phthalimide possessing t-butyl substituent at the para position of 4-benzylpiperazine. This high SHG response may be attributed to the molecular chirality and helical supramolecular frameworks stabilized by C-H center dot center dot center dot O hydrogen bonds in the solid state. The current study attests chiral phthalimides possessing arylpiperazines as effective nominees to the area of crystal engineering and nonlinear optics