Multinuclear Luminescent Schiff-Base Zn−Nd Sandwich Complexes

Abstract

Multinuclear 3d-4f complexes with sandwichlike molecular structures are formed with the Schiff-base ligand bis(3-methoxysalicylidene)ethylene-1,2-phenylenediamine(H(2)L). The stoichiometry and structures are dependent on the Zn:Nd ratio and counteranions present. They are trinuclear [Nd(ZnL)2(NO3)2(H2O)2].NO3.EtOH.H2O (1), [Nd(ZnL)2Cl2(H2O)3].Cl.2MeOH.5H2O (2), and tetranuclear [Nd2(ZnL)2Cl6(MeOH)2].MeOH (3). Dinuclear complex [NdZnL(NO3)3MeCN].MeCN (4) was also characterized. Near-infrared (NIR) lanthanide luminescence is observed in these complexes.

NO3−-induced Salen-based Zn2Yb2 complex with good NIR luminescent property

“…Further from the viewpoint of energy level match, the energy gap ΔE 1 (5188 cm −1 , 1 π-π*-3 π-π*) almost equal to 5000 cm −1 with the effective inter-system crossing [14], together with the relatively suitable energy gap (ΔE 2 = 8418 cm − 1 ) between the ligand-based 3 π-π* excited state and the Yb 3+ ion's first excited state ( 2 F 5/2 , 10,204 cm −1 ), leads to the obtainment of a relatively higher NIR overall quantum yield (Φ L Yb = 0.98%) and an effective quantum efficiency (η sens = 77%; Φ L Yb /Φ Yb Yb ) of complex 2. It is worth noting that the observed NIR lifetime (τ = 25.24 μs) of complex 2 is distinctively longer than those of the reported NO 3 − -templated ZnLn-arrayed [9][10][11] or Zn 2 Ln-arrayed complexes [5], and its quantum efficiency (η sens = 77%) in solution is among the best so far reported Yb 3+ -complexes [15], which should be resulted from quite effective intra-molecular energy transfer besides the complete avoidance of oscillators within the inner coordination sphere of Yb 3+ ions in the Zn 2 Yb 2 -arrayed complex 2.…”

“…For example, stoichiometry-resulted Zn 2 Ln and Zn 2 Ln 2 [5], temperature-dependent Zn 2 Ln and Zn 2 Ln 3 [6], solvent-induced pseudo-polymorphic ZnLn-array [7] or anion-templated discrete-to-polymeric self-assembly [8] [5]. On the other hand, in the obtained ZnLn-or Zn 2 Ln-arrayed complexes, OH-or CH-oscillators of the coordinated solvates around the Ln 3+ ion actually give rise to luminescent quenching at a certain degree.…”

Variety of Crystal Structures of Chiral Schiff Base Lu(III)-Ni(II)/ Cu(II)/Zn(II) and the Related Complexes

“…Moreover, their binuclear complexes containing transition metals and rare earth metals have gained importance from the viewpoint of special interest in photophysical and magnetic properties arising from interactions between metal ions as well as sole metal ions having suitable electronic states or unpaired electrons [8][9][10][11][12][13][14][15][16][17][18][19].…”

Self-assembly as a route to dinuclear lanthanide complexes with rare coordination pattern of salen-type ligand

“…Polynuclear salen-type lanthanide complexes are among them. Contrary to numerous d-block element derivatives of salen-type ligands, structurally defined lanthanide salen-type complexes are rare [13,14,[16][17][18][19][20]. Continuing our interest in searching for new stable complexes of lanthanides [8], we recently communicated the definitive structural details correlated with spectral characterization of the salicylaldimine lanthanide nitrate complexes with an unusual coordination mode [21,22].…”