Syntheses and Studies of Modified Tri-naphthyridyl-di-amine/Tri-pyridyl-di-amine Ligands and Their Metal Complexes
Date Issued
2008
Date
2008
Author(s)
Hsieh, Meng-Hua
Abstract
The aim of this thesis is to investigate the coordination chemistry of three kinds of ligands: di-pyridin-2-yl-benzene-1,3-diamine (H2dpbda) and tetra-pyridin-2-yl-benzene-1,3-diamine (tepbda), and methylated 2,7-Bis(1,8-naphthyridyl)-4-methyl-1,8-naphthyridyl-diamine (H2bnymnyda). The ligands tepbda and H2bnymnyda were synthesized by palladium-catalyzed cross-coupling reactions, and H2dpbda was prepared by an autocatalyzed reaction. With the existence of Cu(II) ions, H2dpbda has been catalyzed to yield the protonated 9-(N-pyridin-2-yl)amino-pyrido[1,2-a]benzimidazole (9-paPBI) product via a N-C coupling reaction. The Ni(II) ions react with tepbda ligands leading to the formation of discrete dinuclear compound [(μ2-tepbda)NiCl2]2, and Cu(II) ions yield to 2D-coordination polymer {[(μ2-tepbda)(CuCl2)2] · CH3OH · 0.5H2O}n, which has weak anti-ferromagnetic interactions (J = −0.75 cm-1). he ligand H2bphany has been used to synthesize the octanickel complexes, [Ni8(μ8-bnymnyda)4Cl2](ClO4)4 and [Ni8(μ8-bnymnyda)4(NCS)2](ClO4)4, where the all syn form ligands have been deprotonated to act as octadentate bridges and were helically wrapped the metal ions to form a linear octanuclear metal string, structurally similar to previous reports. By X-ray structure analysis, we know two-electron reduction occurs on two ends of both metal strings and results in the Ni12+…Ni21+…Ni32+…Ni42+…Ni4׳2+…Ni3׳2+…Ni2׳1+…Ni1׳2+ partial localized arrangements, and Ni1(׳)–Ni2(׳) forms partial bond. The two ends of Ni1(׳)–Ni2(׳) units exhibit anti-ferromagnetic interactions with S = 3/2 character from magnetic studies (μeff ~ 6 B.M.at 300 K), while assuming the inner four nickel ions are in low-spin states (S = 0). The electrochemistry of these complexes displays three reversible redox couples around −0.8 V, −0.5 V, +0.1 V, indicating the reduction states preference. The optically transparent thin-layer electrode (OTTLE) shows both are in good conversions (84.1%−99.8%), so these nickel complexes are stable redox species.
Subjects
metal string
naphthyridine
pyridine
pyrido[1,2-a]benzimidazole
Type
thesis
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