Spectrochimica Acta Part A 79 (2011) 1304–1307 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy jou rn al hom epa ge: www.elsevier.com/locate/saa EPR and optical studies of vanadium doped potassium dihydrogen citrate (C 6 H 7 KO 7 ) single crystal Zeynep Yarbas ¸ i a , Abdulhalik Karabulut a , Bünyamin Karabulut b,∗ a Atatürk University, Faculty of Science and Arts, Physics Department, Erzurum, Turkey b Ondokuz Mayıs University, Faculty of Science and Arts, Physics Department, Samsun, Turkey a r t i c l e i n f o Article history: Received 22 December 2010 Received in revised form 15 April 2011 Accepted 27 April 2011 Keywords: Vanadyl doped EPR Optical studies Potassium dihydrogen citrate a b s t r a c t An EPR and optical studies of VO 2+ doped potassium dihydrogen citrate (PDHC) single crystals have been carried out at room temperature. It crystallizes in triclinic symmetry with the unit cell dimensions: a = 11.343 ˚ A, b = 13.078 ˚ A, c = 6.272 ˚ A, ˛ = 89.79 ◦ , ˇ = 94.36 ◦ ,  = 104.2 ◦ . The angular variation of EPR spectra have shown that two different VO 2+ complexes are located in different chemical environments and each environment contains one magnetically VO 2+ site occupying substitutional position in the lattice and show very high angular dependence. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Citrates have importance for the applications in biological and medical areas [1,2]. Potassium is a mineral that is found in many foods and is needed for several functions of human body, especially in the heart-beat. Potassium citrate is used to treat a kidney stone condition called renal tubular acidosis. Potassium citrate is rapidly absorbed when taken by mouth and is excreted in the urine as the carbonate. It is, therefore, effective in reducing the pain and fre- quency of micturition in the case of high concentration of acidic urine. It is widely used to treat urinary calculi (kidney stones), and is often used by patients with cystinuria. It is well known that the transition metal ions can be used as probe to determine the symmetry environments of the complexes in the host lattices in electron paramagnetic resonance (EPR) tech- nique. VO 2+ ions are used extensively as an impurity probe for EPR studies. Vanadyl complexes have been the subject of interest over resent years [3–18]. When VO 2+ is doped in a diamagnetic crystal as an impurity it forms complexes having various ligands filling its environment. The behavior of the unpaired electron in VO 2+ com- plex is dominated by the strong V O bond. It is also interesting and productive to study the local symmetry and the bonding of the vanadyl complex by correlating EPR and optical absorption data. EPR studies of VO 2+ doped trisodium, diammonium, triammo- nium, tripotassium citrate were reported previously [15–18]. Since there is no study about C 6 H 7 KO 7 in the literature, the EPR investi- ∗ Corresponding author. Tel.: +90 3623121919; fax: +90 3624576081. E-mail address: bbulut@omu.edu.tr (B. Karabulut). gation of VO 2+ doped potassium dihydrogen citrate single crystal is given in this study. 2. Experimental PDHC was purchased from Aldrich. An amount of 0.01 M PDHC was used for preparing each aqueous solution. Vanadium sulfate was used to obtain VO 2+ as dopants. Single crystals of PDHC were grown by slow evaporation at room temperature. Suitable sizes of single crystals for EPR study were obtained within two weeks. The PDHC single crystals belongs to the triclinic system (space group P - 1) and contains two molecules in the unit cell. The unit cell parameters are a = 11.343 ˚ A, b = 13.078 ˚ A, c = 6.272 ˚ A, ˛ = 89.79 ◦ , ˇ = 94.36 ◦ ,  = 104.2 ◦ [19]. An X-Band EPR Spectrometer with 100 kHz modulation field and 9.54 GHz frequency was used for recording EPR spectra in three per- pendicular planes. EPR spectra were recorded at 0–180 ◦ interval of rotation angle with 10 ◦ steps. DPPH with g value 2.0036 is used for determining central field. The optical absorption study was carried out by using Perkin Elmer UV/vis Lambda 2S spectrometer with the wavelength range of 200–1100 nm at room temperature. 3. Results and discussion In this study, the results of EPR and optic absorption investiga- tion of vanadium doped PDHC single crystals are given. The EPR spectra of the VO 2+ doped PDHC single crystal were recorded at ambient temperature for all rotations in three perpendicular planes (a*b, c*a* and bc*) at 10 ◦ steps between 0 ◦ and 180 ◦ , where the c*-axis is perpendicular to the crystallographic b and a* axes. EPR 1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2011.04.059