The effect of ligand design on the structural and photophysical properties of Nd(III) complexes with Schiff bases of the [(phenylimino)methyl]phenol-type

Three mononuclear Nd(III) complexes [Nd(HL₁)₂(NO₃)₃] (<b>1</b>, HL₁=2-methoxy-6-[(<i>E</i>)-(phenylimino)methyl]phenol), [Nd(HL₂)₃(NO₃)₃] (<b>2</b>, HL₂=5-methoxy-2-[(<i>E</i>)-(phenylimino)methyl]phenol) and [Nd(HL₃)₂(NO₃)₃]·CH₃OH (<b>3</b>, HL₃=2-methoxy-6-{(<i>E</i>)-[(2-methoxyphenyl)imino]methyl}phenol) were prepared in a 1:3 ratio (M:L) in methanol. The effect of the ligand substituents and their positions (<i>meta versus para</i>) on the electronic and photophysical properties of the complexes is demonstrated. Single-crystal X-ray diffraction studies show that HL₁ and HL₃ coordinate bidentate <i>via</i> the phenolate and methoxy oxygens, while HL₂ is bound monodentately through the phenolate oxygen, with the coordination environment completed by three <i>η</i>²-chelated nitrates. The significant differences observed in the coordination chemistry of the three Nd(III) complexes provides the opportunity for biological application investigations.

三个单核钕(III)配合物：[Nd(HL₁)₂(NO₃)₃]（配合物1，HL₁=2-甲氧基-6-[(E)-(苯亚氨基)甲基]苯酚）、[Nd(HL₂)₃(NO₃)₃]（配合物2，HL₂=5-甲氧基-2-[(E)-(苯亚氨基)甲基]苯酚）以及[Nd(HL₃)₂(NO₃)₃]·CH₃OH（配合物3，HL₃=2-甲氧基-6-{(E)-[(2-甲氧基苯基)亚氨基]甲基}苯酚），以1:3的金属-配体摩尔比在甲醇中合成。本研究阐明了配体取代基及其取代位置（间位与对位）对该类配合物电子性质与光物理性质的影响。单晶X射线衍射（Single-crystal X-ray diffraction）研究表明，HL₁与HL₃通过酚氧与甲氧基氧以双齿形式配位，而HL₂仅通过酚氧以单齿形式配位，三个η²-螯合硝酸根完成了其配位环境。三种钕(III)配合物在配位化学层面展现出的显著差异，为其生物应用研究提供了宝贵的研究契机。