Synthesis, characterization, electrochemistry and optical properties of new 1,3,5- trisubstituted ferrocenyl pyrazolines and pyrazoles containing sulfonamide moiety Ch. Kiran Kumar a , Rajiv Trivedi a, * , K. Ravi Kumar a , L. Giribabu a , B. Sridhar b a Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500607, Andhra Pradesh, India b X-Ray Crystallography Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500607, Andhra Pradesh, India article info Article history: Received 20 March 2012 Received in revised form 3 August 2012 Accepted 7 August 2012 Keywords: Ferrocene Pyrazoline Pyrazole Sulfonamide Electrochemistry Fluorescence abstract This article describes the synthesis and characterization of a series of new 3-ferrocenyl-1-(4- sulphamylphenyl)-5-aryl-4,5-dihydro-1H-pyrazolines and the corresponding pyrazole derivatives derived from ferrocenyl chalcones and 4-hydrazino benzenesulfonamide hydrochloride. The compounds were characterized by spectroscopic means and the structure of the new ferrocenyl pyrazoline (3a) was determined by means of X-ray crystallography. The optical properties of these compounds were studied by means of UV/visible absorption spectroscopy and fluorescence spectroscopy (both steady state and time-resolved) in dichloromethane solvent. Electrochemical study revealed that all the compounds exhibited reversible oxidation behavior at 521e543 mV corresponding to ferrocene pyrazolines (3ael) and 621e645 mV corresponding to ferrocene pyrazoles (4aej) respectively, as confirmed by the i pc / i pa ¼ 0.92e1.00. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Ferrocene and its derivatives have displayed remarkable inter- disciplinary activities ranging from their applications in material science, catalysis to biological assays [1,2]. Among these derivatives, ferrocene heterocycles containing moieties like condensed imid- azoles [3,4], triazoles [5e8], guanidine [9], oxazoles [10,11], and pyrimidines [12e14] have predominantly attracted remarkable interest due to their widespread applications in various fields of chemistry including medicine [15], supramolecular chemistry [16,17], material science [18,19] and sensors [20]. Pyrazoles and pyrazolines, belonging to one such heterocyclic ring system, have propensity as blue light emitting fluorescent agents with high quantum yields [21e24] and hole transport tendency [25e28]. In recent times, Zhao et al. [29,30], and several others [31,32] have reported on the synthesis, characterization and optical properties of numerous ferrocenyl pyrazoline derivatives. Further, it is well documented that sulfonamide hybrids, an important class of compounds, display a diverse range of biological and photophysical properties [33e37]. These properties are enhanced by attaching the sulfonamide groups within a central substituted planar ring system. Recently Supuran et al., have re- ported on the biological properties of several metallocene based triazoles having sulfonamide derivatives [38], however, reports on ferrocenyl pyrazolines containing sulfonamide group are scarce in the literature. There is an increased interest in the design and synthesis of small molecules exhibiting fluorescent property. Hence, it would be of significant interest to explore a combined influence of the electrochemical property of ferrocene as well as the emission properties of the sulfonamide containing pyrazolines/ pyrazoles in a single hybrid molecule. Herein we report the synthesis, characterization and optical properties of 1,3,5-trisubstituted ferrocenyl pyrazolines and cor- responding pyrazoles containing sulfonamide moiety. While UVe visible, fluorescence spectroscopies and electrochemical analysis were carried out on all these compounds, structure determination using single crystal X-ray crystallography was also done for the compound 3a. 2. Results and discussion 2.1. Scheme of synthesis The synthetic route for the target compounds is outlined in Scheme 1 . The first step involves the base-catalyzed Claisene * Corresponding author. Tel.: þ91 40 27191667. E-mail address: trivedi@iict.res.in (R. Trivedi). Contents lists available at SciVerse ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem 0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jorganchem.2012.08.011 Journal of Organometallic Chemistry 718 (2012) 64e73