FULL PAPER Synthesis, DFT, computational exploration of chemical reactivity, molecular docking studies of novel formazan metal complexes and their biological applications Shakeel Ahmad Khan 1,2 | Komal Rizwan 3 | Sammia Shahid 1 | Mahmoud A. Noamaan 4 | Tahir Rasheed 5 | Hira Amjad 1 1 Department of Chemistry, School of Science, University of Management and Technology, Lahore, 54770, Pakistan 2 Center of Super Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, China 3 Department of Chemistry, Government College Women University, Faisalabad, 38000, Pakistan 4 Mathematics Department, Faculty of Science, Cairo University, Giza, 12613, Egypt 5 School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China Correspondence Shakeel Ahmad Khan, Department of Chemistry, School of Science, University of Management and Technology, Lahore- 54770, Pakistan. Email: shakilahmadkhan56@gmail.com Komal Rizwan, Department of Chemistry, Government College Women University, Faisalabad, 38000, Pakistan. Email: komal.rizwan45@yahoo.com The computational exploration of chemical reactivity and molecular docking of the synthesized formazan compounds (S1-S6) were studied. Further, their antimicrobial activity against bacterial strains (S. epidermidis, B. cereus, K. pneumoniae and P. aeruginosa) and against fungal strains (T. mentagrophytes, C. albicans, A. niger, S. cerevisiae and C. glabrata) using agar diffusion method and antioxidant activity following DPPH inhibition assays were evaluated. Anticancer activity was executed in vitro model of human breast carcinoma (MCF-7) cell line. The superior and enhanced antibacterial and antimycotic activities were exhibited by formazan compound (S4) by presenting maximum ZOIs and MICs values. While enhanced antioxi- dant in terms of percentage inhibition of DPPH and cytotoxic effect on human breast carcinoma-cells demonstrated by formazan compound (S1) which was further validated by the results of molecular docking studies of (S1) with the human estrogen receptor protein. In order to compute quantum chemical reac- tivity descriptors from conceptual density functional theory (CDFT) point of view of this system, including chemical potential (μ), chemical hardness (η), electrophilicity (ω), condensed Fukui function and dual descriptors are calcu- lated at the same level of calculation. The most active sites of these molecules are determined and correlated with experimental data. The present investiga- tion displays that formazans compounds could be potential drug candidate that constrains the growth of microbial strains, possess ability to cause cyto- toxic effect on carcinoma cells and act as effective scavenger for free radical species. KEYWORDS anticancer, antimicrobial, DFT studies, formazan, molecular docking 1 | INTRODUCTION Now days, development of multi-drug resistance in sev- eral bacterial strains including salmonella, streptococci, gonococci, enterococci, staphylococci etc. has become an emerging issue. Besides, some fungi for example Candida species are also displaying resistance to various antifun- gal drugs. [1] Numerous antimicrobial drugs have been developed however; because of the emergence of multidrug-resistance in pathogens, clinical-efficiency of Received: 6 September 2019 Revised: 18 November 2019 Accepted: 26 November 2019 DOI: 10.1002/aoc.5444 Appl Organometal Chem. 2020;e5444. wileyonlinelibrary.com/journal/aoc © 2020 John Wiley & Sons, Ltd. 1 of 24 https://doi.org/10.1002/aoc.5444