FULL PAPER Pyrazine based Pt(II) bis‐alkynyl organometallic complexes: Synthesis, characterization, and cytotoxic effect on A549 human lung carcinoma cells Sourav Bhowmick 1 | Achintya Jana 1 | Subba R. Marri 2 | Prerak Gupta 3 | J.N. Behera 2 | Biman B. Mandal 3 | Neeladri Das 1 1 Department of Chemistry, Indian Institute of Technology Patna, Patna 801 106, Bihar, India 2 School of Chemical Sciences, National Institute of Science Education and Research (NISER), Bhubaneswar 751005, India 3 Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India Correspondence Neeladri Das, Department of Chemistry, Indian Institute of Technology Patna, Patna 801 106, Bihar, India. Email: neeladri@iitp.ac.in; neeladri2002@yahoo.co.in Biman B. Mandal, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, India. Email: biman.mandal@iitg.ernet.in; mandal. biman@gmail.com A facile and efficient synthesis of a series of five new pyrazine‐based organometal- lic complexes is being reported. The complexes (2–6) have been fully characterized. Molecules 2, 3 and 6 were structurally characterized by single crystal X‐ray crystal- lographic analyses. Additionally, anticancer properties of these organometallic com- plexes have been studied against A549 human lung carcinoma cells. Biological studies suggest that complex 5 (with pendant pyridine moieties) exhibited maximal growth inhibitory cytotoxic effect even at lower concentration (nearly 0.5–1 μM) whereas the other four compounds (2, 3, 4 and 6) were non‐toxic below 1 μM concentration. Two complexes (4 and 6) were effective only at higher doses (approx 30 μM) while the remaining two organometallic complexes (2 and 3) were able to inhibit 50% cell growth at slightly lower concentration (nearly 10 μM). As far as IC 50 is concerned, 5 exhibited a minimum value ranging between 3–5 μM which is comparable with cisplatin under similar conditions. KEYWORDS A549 human lung carcinoma cells, anticancer, cytotoxic effect, organometallic complex, pyrazine, X‐ray crystallography 1 | INTRODUCTION Research in the development of new organometallic complexes bearing metal alkynyl linkages has gained much importance since the last decade. [1] The interest in such π‐conjugated metal–organic units is attributed to their potential use as smart materials with applications in the field of electronics, optics, sensors and design of luminescent devices. [2] More importantly, several organometallic complexes have been screened as potential candidates for use in treatment of (lungs) cancer. [3] The need to develop new anticancer compounds stems from the fact that widely used platinum based drugs (cisplatin, carboplatin and oxaliplatin) have several drawbacks that include but are not limited to undesirable harmful side‐effects and antitu- mor activity with a relatively narrow spectrum. [4] In this context, it may be mentioned that polynuclear platinum complexes may be considered as alternative drugs to cisplatin (and its derivatives) with the objective to widen the spectrum of platinum based anticancer drugs concomi- tantly reducing the other side effects. [5] As far as organometallic complexes with multiple plati- num centers are concerned, several organic motifs such as anthracene, phenanthrene, carbazole, fluorene, truxene, iptycene, oxadiazole, and others have been incorporated. [6] Recently, we have reported Pt(II) organometallic complexes derived from 2,6‐dichloropyrazine as a precursor unit. [7] This current research interest, i.e., development of pyrazine unit Received: 16 January 2017 Revised: 3 March 2017 Accepted: 4 March 2017 DOI: 10.1002/aoc.3824 Appl Organometal Chem. 2017;e3824. https://doi.org/10.1002/aoc.3824 Copyright © 2017 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/aoc 1 of 11