Chemical Physics Letters 645 (2016) 59–70 Contents lists available at ScienceDirect Chemical Physics Letters jou rn al hom epage: www.elsevier.com/locate/cplett Biological applications and spectroscopic investigations of 4-nitrophenol-urea dimer: A DFT approach T. Joselin Beaula a , P. Muthuraja b , M. Dhandapani b , I. Hubert Joe c , V.K. Rastogi d , V. Bena Jothy a,∗ a Department of Physics and Research Centre, Women’s Christian College, Nagercoil 629 001, Tamil Nadu, India b Post Graduate and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore 641020, Tamil Nadu, India c Department of Physics and Research Centre, Mar Ivanios College, Nalancira 695015, Kerala, India d Indian Spectroscopy Society, KC 68/1, Old Kavinagar, Ghaziabad 201 002, India a r t i c l e i n f o Article history: Received 23 October 2015 In final form 14 December 2015 Available online 21 December 2015 a b s t r a c t Molecular geometry of grown crystal 4-nitrophenol-urea has been evaluated and compared with XRD data while the crystalline nature of the compound has been confirmed by PXRD study. Vibrational analysis has been performed using NCA and dielectric studies have been carried out at room temperature. NBO analysis has been applied in comparative study of charge delocalization. Molecular orbital contributions have been investigated by TDOS and DOS. Enhancement of microbial treatments against bacteria and fungi has been assessed and a remarkable efficiency has been recorded. © 2015 Elsevier B.V. All rights reserved. 1. Introduction 2-Nitrophenol is used mainly as an intermediate for the pro- duction of dyestuffs, pigments, rubber chemicals and fungicides. However 4-nitrophenol is used as a laboratory reagent, fungicide in military footwear, precursor for the preparation of phenetidine and acetophenetidine, indicators and raw materials for fungicides. Fluorine substituted nitrobenzene is used to produce pharma- ceutical drugs and agrochemical products [1,2]. Though urea has shown interesting NLO applications, it is well known that it is a functional moiety commonly found in natural products and often displays a wide range of biological activities which is reported in literature to possess antibacterial, antifungal, anticonvulsant, anti- cancer activities, etc. [3]. Crystal structure and characterization of 4-nitrophenol-urea (4NPU) have already been reported [4]. N,N-(3- nitrophenyl) urea is used as an anti-solvent to increase the yield of adducts. In the past three decades, urea has been offered an open choice to be a novel material for extensive theoretical and experimental study due to its interesting physical and chemical properties [5,6]. Metal–urea complexes have pharmaceutical appli- cations too; the platinum–urea complex is used as antitumor [7]. In view of these considerable importance, the present work, intends ∗ Corresponding author. E-mail address: benaezhil@yahoo.com (V.B. Jothy). to fully exploit the synthesis, spectral, electrical and biological char- acterization of 4NPU along with the DFT calculations to investigate molecular geometry and electronic structure. 2. Experimental details Powder XRD data have been collected in Bruker AXS instrument model D8 advance instrument using CuK radiations ( = 1.5406). FT-IR spectrum in the region 4000–400 cm -1 has been recorded using Perkin Elmer one: FT-IR Spectrometer with a typical resolu- tion of 1.0 cm -1 . FT-Raman spectrum in the region 4000–50 cm -1 has been recorded using Bruker RFS 27: Stand alone FT-Raman Spectrometer with Nd:YAG laser source at 1064 nm and resolution 2 cm -1 . UV–visible absorption spectrum of solid material has been measured in JASCO (V-570) UV/VIS/NIR spectrometer. Dielectric study has been recorded using 3532-50 LCR meter and antimicro- bial activity has been screened by agar well diffusion method. 3. Theoretical methodology DFT computation has been performed using gaussian'09 pro- gram package [8] with B3PW91 as the standard 6-311++G(d,p) basis set. Total energies for cyclic dimers have been corrected for basis set superposition error (BSSE) [9]. Natural bond orbital (NBO) analysis [10] has been performed using nbo 3.1 program to under- stand inter- and intra-molecular bonding and interaction among http://dx.doi.org/10.1016/j.cplett.2015.12.029 0009-2614/© 2015 Elsevier B.V. All rights reserved.