ORIGINAL ARTICLE Synthesis and Crystallographic, Absorption and Emission Studies of 4-Pyridine Carboxamide of Zn(II) 4-Chlorophenylacetate Füreya Elif Özbek 1 & Mustafa Sertçelik 1 & Mustafa Yüksek 2 & Güventürk Uğurlu 3 & Ali Murat Tonbul 4 & Hacali Necefoğlu 4,5 & Tuncer Hökelek 6 Received: 27 May 2019 /Accepted: 10 September 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract A new zinc(II) complex, [Zn(CB) 2 (INA) 2 ] (where CB is 4-chlorophenylacetate and INA is 4-pyridine carboxamide) was synthesized. The structure of the complex was characterized by elemental analysis, FT-IR spectroscopy and single-crystal X- ray diffraction technique. Besides, the thermal stability of the complex was investigated by TGA/DTA analysis method. Moreover, the optical absorption and the emission features of the complex were examined by using UV-Vis and fluorescence spectrophotometers, respectively. Furthermore, Density Functional Theory (DFT) calculations were carried out to support the experimental results. Accordingly, it was determined that the complex crystallized in a monoclinic system with space group Pc, a = 8.3329 (2) Å, b = 25.6530 (4) Å, c = 13.5048 (3) Å, α = 90°, β = 91.703 (3)° and γ = 90°. The complex consists two crystallographically independent molecules. In each molecule, the Zn II ion adopts a distorted trigonal pyramidal coordination formed by two O atoms from the two 4 chlorophenylacetate ligand and two N atoms of the two 4-pyridine carboxamide ligands. It was observed that the linear absorption spectra of the complex were similar to linear absorption spectra of the semiconductors. In addition, two emission peaks were observed in the fluorescence spectra which could be due to the formation of excimer and the interactions of the benzene and pyridine rings. The energy gap (ΔE gap =E LUMO -E HOMO ) of the complex has been calculated as 3.712 eV and this value is very close to the experimentally measured value (3.86 eV). Therefore, because of higher fluorescence intensity of emission peak that was observed between 309 and 556 nm wavelength besides other traits, the complex could potentially be used in the blue light OLED application by filtering of the emission peak around 710 nm wavelength. Keywords Zn complex . 4-Chlorophenylacetic acid . Optical absorption . Fluorescence . DFT Introduction Scientists have spent much effort in coordination chemistry for more than a century to synthesis new complexes with transition metals for fluorescence [1–3], catalysis [4–6], elec- trochemistry [7], antibacterial [8, 9], chemical sensors [10, 11], electronic devices [12–14], nonlinear optic [15–17] and gas adsorption [18] applications. The complexes which are exhibited fluorescence behavior have a wide application area such as: (i) protein detecting with high sensitivity [14], (ii) nitroaromatic explosive detecting [19], (iii) DNA sequencing [20]. The purpose of the crystal engineering is to explore new materials with particular interest which can be used in various application areas. In this context, the structures, biological and physical properties of the complexes are affected by metal ions, ligands in the coordination, and intermolecular interac- tions. When these intermolecular interactions are examined, it Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10895-019-02440-x) contains supplementary material, which is available to authorized users. * Füreya Elif Özbek fozturkkan36@gmail.com 1 Department of Chemical Engineering, Kafkas University, 36100 Kars, Turkey 2 Department of Electrical and Electronic Engineering, Kafkas University, 36100 Kars, Turkey 3 Department of Physics, Kafkas University, 36100 Kars, Turkey 4 Department of Chemistry, Kafkas University, 36100 Kars, Turkey 5 International Scientific Research Centre, Baku State University, 1148 Baku, Azerbaijan 6 Department of Physics, Hacettepe University, 06800 Beytepe, Ankara, Turkey Journal of Fluorescence https://doi.org/10.1007/s10895-019-02440-x