Journal
JOURNAL OF PHYSICAL CHEMISTRY A
Volume 107, Issue 39, Pages 7879-7884Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp034971n
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Experimental and theoretical study of nuclear magnetic resonance (NMR) spectra of dinuclear complexes of paramagnetic trivalent Tb, Dy, Ho, Er, Tm, or Yb ions with phthalocyanine ligands is presented. The H-1 NMR paramagnetic shifts of the dinuclear Pc triple-decker complexes PcLnPcLnPc* (abbreviated as [Ln, Ln]; Pc is the dianion of phthalocyanine and Pc* is the dianion of 2,3,9,10,16,17,23,24-octabutoxyphthalo-cyanine) were measured in CDCl3 solution at 303 K. These values are analyzed using the corresponding data of two series of heterodinuclear complexes with a single paramagnetic ion, namely PcYPcLnPc* ([Y, Ln]) and PcLnPcYPc* ([Ln, Y]). The paramagnetic shifts in [Y, Ln] and [Ln, Y] were reproduced solely by the magnetic dipolar (pseudo-contact) term, using a geometric structure that was obtained by a density functional theory (DFT) calculation with a moderate modification. Each paramagnetic shift value of [Ln, Ln] is shown to be sum of those of [Y, Ln] and [Ln, Y]. The independence of the paramagnetic shift contributions of the two Ln ions is explained by the small interaction between f-electronic systems in [Ln, Ln]. The shifts in an [Ln, Ln] complex have the same sign, because all the protons are positioned in the same region of the contour map of the dipolar contributions of the two paramagnetic sites.
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