(1)十一核鎳金屬串與(2)聯苯萘啶胺三核金屬串的異構物之性質探討

Abstract

In this study, we report the new generation linear undeca-nickel mixed-valence metal string complexes with modified naphthyridylamide ligands. The single-molecular conductance 5.76 x 10-5 G0 was measured by STM-BJ method. That is the first measurements of undecanickel chain with unidirectionally order; the trinuclear Mo/Ni, Co, Zn heterometallic string complexes with Hbphany ligand, and investigate the properties of them by X-ray diffraction, cyclic voltammetry and SQUID. Undeca-nickel mixed-valence metal string complexes, [Ni11(bnatpya)4Cl2](PF6)2Cl2 1、[Ni11(bnatpya)4Cl2]Cl2 2 and [Ni11(bnatpya)4(NCS)2](PF6)2Cl2 1a, are synthesized with the modified H4bnatpya ligand. The magnetic measurement of 1 reveals that antiferromagnetic interactions between the two termini independent high-spin nickel(II) ions (J = -0.23 cm-1). The two-electron reduction of 1 leading to generation of 2 ([Ni11]20+). The mixed valence unit of naphthridyls ([Ni2(napy)4]3+) in 2 with three partially delocalized unpaired electrons; a shorter spin-spin distance confers a stronger antiferromagnetic interaction (J = -0.93 cm-1). The complex 1 displays two pairs of redox waves, the peak of E1/2 at +0.11 V and +0.30 V are attributed to the redox reaction of [Ni11]22+/20+ and [Ni11]23+/22+, respectively. The first measurements of single-molecule conductance of 1a are 5.76 x 10-5 G0; however, it does not follow the mechanism of direct tunneling. Further works are required to explore the conduction mechanism of metal strings. Surface analysis were obtained by ultrahigh vacuum scanning tunneling microscope (UHV-STM), from the STM images, which show that the electron cloud of single metal string molecule exhibits a left-handed or right-handed configuration with an angle of about 50o between the metal axis and the helical electron cloud. In addition, it is observed that the electron cloud of some molecules reveal non-left and right hand but rather about 90o with the metal axis. In second part, three tri-homometal strings [Ni3(bphany)4X2] (X = Cl- (3a), NCS- (3b, 3c)) and six tri-hetreometal strings [Mo2M(bphany)4X2] (M = Ni (4a, 4b); Co (5a, 5b, 5c); Zn (6)), supported by four bphany ligand have been synthesized, and characterized. Since the ligand is a symmetrical, the metal strings may have several different isomeric forms. By the steric effect of terminal chloride ions and bulky biphenyl group, complexes 3a, 4a, 5a and 6 are adopt a unique (4,0) arrangement. When asymmetrical ligand deprotonation, the charge distribution on nitrogen are different. We can control the metal bonding site to overcome the crystallographic disorder problem. As the asymmetry of the ligand is increased to increase the solubility of the molecule, the different isomers can be separated by column chromatography.