The Formation Mechanism of Assembled Complexes Bridged by 1,3–Bis(4–Pyridyl)Propane

Abstract

Abstract. Several types of differently coloured crystals (light blue, blue and red) were obtained in the synthesis of assembled complex of mixed crystals with three metals by using solvent diffusion method. The mechanism of obtaining the assembled complexes is discussed based on the structure and colour change. The red crystal has 2D interpenetrated structure. Keywords: mixed crystal, assembled complex, 1,3-bis(4-pyridyl)propane, crystal formation. IntroductionSelf-assembled coordination polymers containing transition metal ions and organic bridging ligands have attracted intensive interest in virtue of their potential abilities for selective inclusion and transformation of ions and molecules [1]. Up to now various assembled structures have been reported [2][3][4][5][6][7][8]. We have studied iron complexes bridged by 1,3-bis(4-pyridyl)propane (bpp), containing three methylene groups, by using single crystal X-ray diffraction analysis, Mössbauer spectroscopy and Superconducting Quantum Interference Device (SQUID) measurements. Fe(NCX) 2 (bpp) 2 (X = S, Se and BH 3 ) had a 2D interpenetrated structure and the NCBH 3 complex showed a spin-crossover phenomenon [9]. When the benzene is enclathrated, the structure becomes 1D chain [10]. Recently, we discussed the spin state of the mixed crystals of iron with zinc or cobalt ion in the 2D interpenetrated structure for the assembled complexes bridged by bpp, and we revealed that NCSe complex had a lowered spin state, in comparison with pure Fe complex, because iron atom is forced to reduce its radius in the zinc or cobalt complexes having smaller unit cell [11].Herein we report on the synthesis of mixed crystals including zinc, cobalt, and iron atoms. Several types of crystals appeared and the colour changed in the reaction medium. The mechanism of obtaining the assembled complexes is put into discussion on the basis of structure and colour modifi cation.