Solvent-Induced Polymorphism in a Schiff Base Compound and Their Distinguishing Effects on Semiconducting Behaviors for Utilization in Photosensitive Schottky Devices

abstract

The capacity to selectively tune the optical and electrical properties of organic molecules has emerged as an effective strategy for the development of flexible optoelectrical devices. These physical properties are influenced by crystal packing, and as a result, they are expected to vary with polymorphic modifications. Herein, we illustrate the pivotal influence of polymorphism on the optoelectronic traits of the resulting solids, paving the way for prospective applications such as photosensitive Schottky devices. In this study, we isolated two distinct color polymorphs, denoted as I and II, of a novel Schiff base, (E)-2-methoxy-4-methyl-6-((3-nitrophenyl)iminomethyl)phenol, obtained from the condensation reaction between 2-hydroxy-3-methoxy-5-methylbenzaldehyde and m-nitroaniline. These polymorphs I and II were obtained in pure crystalline forms using different solvents, namely, acetonitrile and methanol, respectively. Analysis via X-ray crystallography unveiled that both forms I and II crystallize within the orthorhombic unit cell, albeit with different space groups of P2(1)2(1)2(1) and Pca2(1), respectively. Notably, the nitro group in these polymorphic forms establishes distinct noncovalent interactions, ensuring the selective stability of each polymorphic form in the solid state with discernible contributions from the solvents. Furthermore, polymorphs I and II exhibited reversible thermochromic behaviors between room temperature and low temperature (77 K). Electrical conductivity and photosensitivity studies of the polymorphs revealed that the electrical properties of these polymorphs are significantly different, with notable enhancements observed, particularly for form II, upon illumination with visible light. Our results overall highlight the potential of polymorphic design as a promising avenue for fine-tuning the optoelectrical properties of organic crystalline materials, thereby opening avenues for their utilization in the fabrication of photosensitive devices.

keywords

GENERALIZED GRADIENT APPROXIMATION; CONFORMATIONAL POLYMORPHISM; CRYSTAL; DIODE

subject category

Chemistry; Crystallography; Materials Science

authors

Jana, NC; Halder, S; Brandao, P; Ray, PP; Chowdhury, B; Ortega-Castro, J; Frontera, A; Panja, A

Groups

G1 - Porous Materials and Nanosystems

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

A.P. gratefully acknowledges the financial support of this work by the Government of West Bengal through the Department of Science & Technology and Biotechnology, Kolkata, India (Sanction No. 331/ST/P/S&T/15G-8/2018, dated 19.06.2019). P.B. gratefully acknowledges the financial support of this work by the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC). We also acknowledge the MICINN/AEI of Spain (10.13039/501100011033, project TED2021-130946B-100) for financial support.