Thiocyanate mediated structural diversity in phenol based “end-off” compartmental ligand complexes of group 12 metal ions: Studies on their photophysical properties and phosphatase like activity Jaydeep Adhikary a,b , Prateeti Chakraborty c , Sugata Samanta d , Ennio Zangrando e , Sanjib Ghosh f , Debasis Das a, ⁎ a Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India b Department of Chemical Sciences, Ariel University, Ariel 40700, Israel c Department of Chemistry, School of Basic Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh 201306, India d Department of Chemistry, Presidency University, Kolkata 700073, India e Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy f The School of Science, Adamas University, Barasat, West Bengal, India abstract article info Article history: Received 11 November 2016 Received in revised form 30 December 2016 Accepted 22 January 2017 Available online 25 January 2017 The reaction of a pentadentate compartmental ligand LH, namely 4-tert-Butyl-2,6-bis-[(2-pyridin-2-yl- ethylimino)-methyl]-phenol, with group 12 metal ions (Zn II , Cd II , Hg II ) followed by addition of NaSCN afforded one discrete dinuclear complex [Zn 2 (L)(SCN) 3 ](1), and two polymeric 1D species [Cd 2.5 (L)(SCN) 3 (AcO)] n (2) and [Hg 2 (L)(SCN) 3 ] n (3). All the complexes have been structurally characterized by single crystal X-ray diffrac- tion. The crystal structure of the complexes reveals different coordination modes of thiocyanate anion that affect the different topology detected in the compounds: the anions are μ 1 -NCS and μ 1,1 -NCS connected in complex 1, while μ 1,3 -NCS bridging mode is observed in 2, and μ 1 -SCN and μ 1,3 -NCS in 3. The polymeric Hg complex of the bicompartmental ligand system here reported is unprecedented. Detail study of their photophysical properties including the phosphorescence spectra at 77 K has been done. Phosphatase like activity of all the three complexes has been performed in DMSO-H 2 O medium and their activity follows the order of 1 N 2 NN 3. © 2017 Elsevier B.V. All rights reserved. Keywords: Coordination chemistry Group 12 metals Structural diversity Photophysical property Phosphatase like activity 1. Introduction It is well-known that inorganic-organic hybrids of mono- and dinu- clear complexes as well as of polymeric species, especially those with [d 10 ] metal centers, [1–10] exhibit photoluminescence and have poten- tial applications as optoelectronic devices [11–13]. Exploiting the differ- ent varieties of coordination geometries around these metal ions, diverse molecular and crystalline architectures [14,15] of different shapes and sizes [16] may be accessed through strong metal–ligand covalent bonds [17] and multiple weak non-covalent forces [18–21]. The presence of the [d 10 ] electronic configuration hampers to apply the analytical tech- niques such as Mossbauer, EPR spectroscopy and magnetic susceptibility measurements for their detection. On the other hand, emission spectros- copy can be fruitfully used because group 12 metal complexes change the fluorescence intensity of organic fluorophores containing coordinated center [22–26] and therefore fluorescence spectroscopy [22] has been the most powerful tool to detect these metal ions [24–26]. Schiff bases [27–29] have recently been focused by coordination chemists due to their preparative accessibilities, structural varieties and varied denticities. Additionally pseudohalide anions like ambidentate thiocyanate [8,30–34] result in different molecular architectures through their versatile ligation modes (Fig. 1). Combining these two features we have synthesized three thiocyanate bridged Schiff base complexes, namely [Zn 2 (L)(SCN) 3 ](1), [Cd 2.5 (L)(SCN) 3 (AcO)] n (2), [Hg 2 (L)(SCN) 3 ] n (3), where LH = 4-tert- Butyl-2,6-bis-[(2-pyridin-2-yl-ethylimino)-methyl]-phenol (Scheme 1). All three complexes have been structurally characterized showing that complex 1 is a discrete dinuclear species, whereas 2 and 3 are polymeric in nature. The different coordination modes of ambidentate thiocyanate to the [d 10 ] metal ions lead to diverse complex nuclearity, which may be explained by the age-old hard and soft acids and bases (HSAB) theory [35]. Comprehensive investigations of photophysical properties of the complexes in solution as well in solid state have been executed. The catalytic cleavage of phosphoesters is a fundamental reaction for living organisms, such as in processing RNA replication and bone me- tabolism, and it is of ecological significance in the detoxification of pes- ticides. Natural phosphatases, which accomplish this hydrolysis, commonly contain zinc (II) ions in their active sites. Zinc (II) ion is fre- quently chosen by nature due to its high Lewis acidity, flexibility of Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 178 (2017) 114–124 ⁎ Corresponding author. E-mail addresses: pchemsg@gmail.com (S. Ghosh), dasdebasis2001@yahoo.com (D. Das). http://dx.doi.org/10.1016/j.saa.2017.01.041 1386-1425/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa