Third-order nonlinear optical investigations of meso-tetrakis(2,3,5,6- tetrafluoro-N,N-dimethyl-4-anilinyl)porphyrin and its metal complexes N.K. Siji Narendran a , Rahul Soman b , Chellaiah Arunkumar b , K. Chandrasekharan a,⇑ a Laser and Nonlinear Optics Laboratory, Department of Physics, National Institute of Technology Calicut, Kozhikode 673601, Kerala, India b Bioinorganic Materials Research Laboratory, Department of Chemistry, National Institute of Technology Calicut, Kozhikode 673601, Kerala, India highlights  We examined the third order NLO properties of a series of metallo porphyrins.  Techniques used were Z-scan and degenerate four wave mixing.  The v (3) values are increasing with the d-shell occupancy of central metal atoms.  Electrostatic potential (ESP) mapping is done to know electron density changes.  The results obtained are in accordance with the ESP plots. graphical abstract article info Article history: Received 19 June 2014 Received in revised form 4 September 2014 Accepted 23 September 2014 Available online 7 October 2014 Keywords: Nonlinear optics Z-scan Optical limiting Degenerate four wave mixing abstract We report here the experimental investigation on third-order nonlinear optical parameters of 5,10,15,20- tetrakis(2,3,5,6-tetrafluoro-N,N-dimethyl-4-anilinyl)porphyrin and its various metal complexes, using Z-scan technique at 532 nm. The third-order nonlinear optical susceptibilities (v (3) ) were of the order 10 12 esu and are compared through degenerate four wave mixing (DFWM). The operating mechanism is reverse saturable absorption (RSA) as the effective excited-state absorption cross-section was found higher than ground state absorption cross-section as well as the magnitude of nonlinear absorption coef- ficient was found decreasing with on-axis input intensity. The compounds found to exhibit good optical limiting at 532 nm, 7 ns excitation steering applications in laser safety. Ó 2014 Elsevier B.V. All rights reserved. Introduction A remarkable growth of research in the field of nonlinear optics has been ensued in the last few decades. Efforts from physicists, chemists and material scientists are still going on to understand the basic processes responsible for the nonlinearity of various conjugated polymers, organic compounds, organometallic com- pounds, metal polymer composites etc. [1–4]. Materials with prominent p-electron delocalization like organic compounds and organometallic complexes have received significant attention due to their large and quick nonlinear response and potential applica- tions in optical limiting, optical data processing, communication, optical switching, etc. [5,6]. Recent research emphasis is on the rational design and synthesis of novel chemical structures that can be sewed to optimize the nonlinear response without compro- mising their chemical, mechanical, optical and thermal stability. Among the various organic materials, porphyrins and metallo- porphyrins are the most studied group of molecules [7,8] since a significant enhancement of hyperpolarizability can be achieved through metal insertion at the ring center or by functionalization at the peripheral positions [9,10]. The basic skeleton of the http://dx.doi.org/10.1016/j.saa.2014.09.102 1386-1425/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: csk@nitc.ac.in (K. Chandrasekharan). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 838–844 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa