Quantum chemical perspective of efficient NLO materials based on dipolar trans-tetraammineruthenium (II) complexes with pyridinium and thiocyanate ligands: First theoretical framework Muhammad Ramzan Saeed Ashraf Janjua a,b,⇑ , Saba Jamil b , Tauqeer Ahmad b , Zhihua Yang a , Asif Mahmood b , Shilie Pan a,⇑ a Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Technical Institute of Physics & Chemistry of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, 40-1 South Beijing Road, Urumqi 830011, China b Department of Chemistry, University of Sargodha, Sargodha, Pakistan article info Article history: Received 25 November 2013 Received in revised form 28 January 2014 Accepted 29 January 2014 Available online 6 February 2014 Keywords: Tetraammineruthenium Acceptor CAM-B3LYP Hyperpolarizability NLO abstract In this research work non-linear optical (NLO) properties of dipolar trans-tetraammineruthenium (II) complexes with pyridinium and thiocyanate ligands have been calculated by using density functional theory (DFT). For reference systems, four functionals B3LYP, PBE0, BHandHLYP and CAM-B3LYP were employed to select the best functional to study designed compounds on the basis of similarity between calculated and experimental results. The calculated static hyperpolarizabilities were found to be strongly functional dependent. The results from CAM-B3LYP seem to be more reliable when compared to the available experimental data. Thus, new compounds have been theoretically designed by the substitution of electron withdrawing atom/groups as acceptor on reference systems. All the designed compounds dis- play intense band due to metal-to-ligand charge transfer (MLCT). The second-order polarizability has shown a remarkable increase on substitution of strong electron withdrawing atom/groups as an acceptor. The second-order polarizability of all the designed systems was high calculated to be 185  10 30 to 842  10 30 esu. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Atomic, molecular, solid-state physics, surfaces interface sciences; materials science, medicine, chemical dynamics and biophysics are diverse disciplines in which non-linear optical materials have been used. In recent years, due to advances in laser technology, non-linear optics (NLOs) has become a field of major study [1a]. Theoretical studies on non-linear optical materials have attracted much attention recently to pave the way for the experi- mentalists to synthesize new materials [1b–p]. Designing, development and search of NLO materials have become very important during recent years due to potential appli- cations in optical limiting devices, optical bistability, high-speed all optical switches, optical signal processing and computing [2]. Criterion of large hyperpolarizability is being applied in the search of NLO metal complexes [2]. Organo-metallic complexes of transition metals, beside the very good non-linear optical properties, have other characteristics, such as low dielectric constants, ultrafast response times, good process- ability as thin-film devices, and enhanced nonresonant responses. All the properties combine to make them as a suitable candidate for multifunctional materials development [3]. Organometallic compounds also show strong absorptions in UV/Vis regions as compared to organic molecules due to metal-to-ligand and li- gand-to-metal charge transfer [4]. In this work, we have studied the non-linear optical properties of dipolar trans-tetraammineruthenium (II) complexes, which con- tain pyridinium and thiocyanate ligands. New high NLO response compounds have designed by the introduction of acceptors (F, CF 3 and CN) in tetraammineruthenium (II) complexes. Non-linear optical properties and UV/Vis spectra of designed compounds were calculated. Natural bonding orbitals (NBO) analysis was also performed to study the charge transfer. This quantum chemical perspective will pave the way for the experimentalists to develop high performance optical materials in future. This work may http://dx.doi.org/10.1016/j.comptc.2014.01.031 2210-271X/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. Addresses: Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Technical Institute of Physics & Chemistry of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, 40-1 South Beijing Road, Urumqi 830011, China, Department of Chemistry, University of Sargodha, Sargodha, Pakistan (M.R.S.A. Janjua). E-mail addresses: Janjua@uos.edu.pk, Dr_Janjua2010@yahoo.com (M.R.S.A. Janjua), slpan@ms.xjb.ac.cn (S. Pan). Computational and Theoretical Chemistry 1033 (2014) 6–13 Contents lists available at ScienceDirect Computational and Theoretical Chemistry journal homepage: www.elsevier.com/locate/comptc