A new polymorph of 5-bromo ortho vanillin: Synthesis, characterization, crystal engineering, Hirshfeld surface, calculation of interaction energy, and energy frameworks

Abstract

This article reports on one of the newly synthesized 5-bromo ortho vanillin (C₈H₇BrO₃) (1) polymorphs, whose X-ray structure was determined by single crystal X-ray diffraction. The polymorph attains a monoclinic system, space group P2₁/c, V = 824.3(9), and Z = 4. In this work, the cell parameters observed are a = 4.080(2) Å, b = 20.733(12) Å, c = 9.844(7) Å, and β = 98.4(2). Polymorph 1 is compared with the reported compound 2. The article discusses the structural characterization of polymorph 1 using HRMS, FTIR, UV-vis, ¹H/¹³C NMR, and ¹³C DEPT NMR spectroscopy, and explores NCSI (noncovalent supramolecular interactions) within the crystal network. Furthermore, the Hirshfeld surface and 2D fingerprint plot analyze the presence of significant H···Br (20.8%) and H···O (23.8%) contacts in the crystal assembly. In addition, interaction energies and energy frameworks have been calculated. The study revealed that the constructed frameworks fall into electrostatic (E_ele, red cylinders) and dispersion (E_dis, green cylinders) categories, along with total interaction energies (E_tot, blue cylinders). The polymorph is rationalized using physicochemical, crystallographic, Hirshfeld surface, interaction energy and energy frameworks.