Journal of Crystal Growth 304 (2007) 435–440 Growth and characterization of organometallic nonlinear optical TMTM single crystals K. Rajarajan b , Preema C. Thomas a , I. Vetha Potheher a , Ginson P. Joseph a , S.M. Ravi Kumar a , S. Selvakumar c , P. Sagayaraj a,Ã a Department of Physics, Loyola College, Chennai 600 034, India b Department of Physics, R.V. Govt. Arts College, Chengalpattu 603 001, India c Department of Physics, Sathyabama Institute of Science and Technology, Chennai 600 119, India Received 4 November 2006; received in revised form 17 February 2007; accepted 5 March 2007 Communicated by M. Roth Available online 24 March 2007 Abstract Nonlinear optical single crystal of tetrathiourea mercury (II) tetrathiocyanato manganate (II)—Hg(N 2 H 4 CS) 4 Mn(SCN) 4 (TMTM)— was conveniently grown by slow evaporation technique. The cell parameters of TMTM single crystals were confirmed by single crystal X- ray diffraction. The grown crystals were subjected to optical characterization by FT-IR, FT-Raman and UV–vis–NIR techniques. Thermal studies suggest that TMTM undergoes three stages of decomposition and is thermally stable up to 199.06 1C. r 2007 Elsevier B.V. All rights reserved. Keywords: A1. Optical; A1. Thermal; A2. Solution growth; B1. Organometallic; B2. Nonlinear optic 1. Introduction Nonlinear optics is a fascinating field, which plays a major role in the emerging photonics and optoelectronics. New nonlinear optical (NLO) frequency conversion materials have a significant impact on laser technology, optical communica- tion and optical data storage. Organometallic materials have the potential for combining the high optical nonlinearity and chemical flexibility of organics with the physical ruggedness of inorganics [1–3]. Recently, the coordination compounds formed by thiourea and thiocyanate ligands and metal (II) ion have received wide attention due to their superior optical and physical properties. In this category of materials, thiourea as a ligand possesses a large dipole moment and has the ability to form extensive network of hydrogen bonds [4] whereas SCN, as a bidentate ligand, is a good chromophore to enhance the SONLO properties [5]. In the present work, attempts are made to combine thiourea and thiocyanate ligands with the transition metal ions Hg 2+ and Mn 2+ . The organometallic NLO crystals of tetrathiourea mercury (II) tetrathiocyanato manganate (II), Hg(N 2 H 4 CS) 4 Mn(SCN) 4 (abbreviated as TMTM), are grown in mother solvent using slow evaporation technique. The crystal structure of TMTM has been reported recently by Yu et al. [6]. TMTM crystallizes in non-centrosymmetric space group I4 ¯ with tetragonal crystallographic system. In the present work, we report the growth of TMTM single crystals in bulk size for the first time and its characterization by single crystal XRD, FT-IR, FT- Raman, UV–vis–NIR, TG–DTA and DSC studies are also reported. 2. Experimental procedure 2.1. Synthesis and crystal growth TMTM was synthesized by taking appropriate amount of N 2 H 4 CS, KSCN or NH 4 SCN and HgCl 2 were dissolved in an aqueous solution. All the chemicals were highly pure and used as purchased. The reaction formula is 4ðN 2 H 4 CSÞþ 4ðXSCNÞþ HgY 2 þ MnY 2 ! HgðN 2 H 4 CSÞ 4 MnðSCNÞ 4 þ 4XCl; ARTICLE IN PRESS www.elsevier.com/locate/jcrysgro 0022-0248/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2007.03.005 Ã Corresponding author. Tel.: +91 44 22490490; fax: +91 44 28231684. E-mail address: psagayaraj@hotmail.com (P. Sagayaraj).