Syntheses, structures and photophysical properties of tetranuclear Cd–Ln coordination complexes

Abstract

Four novel hetero-tetranuclear d-f coordination complexes, [Ln2Cd2(p-toluylate)10(phen)2] (Nd, 1; Pr, 2; Sm, 3) and [Ho2Cd2(p-chloro-benzoate)10(phen)2](4) (phen = 1, 10-phenanthroline), are synthesized by the hydrothermal method, and their structures are studied by single-crystal X-ray diffraction. Structures 1-3 are isomorphous and structure 4 has a similar molecular structure. In the near-infrared (NIR) region or in the visible region, complexes 1-4 show the characteristic emission bands of Ln(III) ions, which are attributed to the sensitization from the ligands and d-block (cadmium-ligand section) to f-block (lanthanide-ligand section). Moreover, in the Cd-Ln complexes, the CdLn separation is very close, so the d-orbital of the Cd(II) ion and the f-orbital of the Ln(III) ion may influence each other, which probably cause the intra-levels to be adjusted. This can have a significant effect on the emission bands in the NIR region, hence the corresponding emission bands of complexes 1, 2 and 4 exhibit shift or splitting compared with isolated Ln(III) ions. At the same time in the UV-Vis-NIR absorption spectra of the complexes, the corresponding absorption bands also show shift or splitting. The shift or splitting of bands in the NIR emission spectra and in the absorption spectra can evidence each other.

Yb(III), Sm(III) and La(III) complexes of a tetradentate pyridoxal Schiff base ligand: Their DNA-binding activity and bio-imaging applications

“…A broad peak centred around 430nm in the free ligand is assigned n→π* transition and this band is absent in the complexes. For the Sm(III) complex two transitions at 955 nm and 1080 nm are assigned to f-f transitions ( 6 H5/2 → 6 F11/2, 6 F9/2) (Figure S8) [56,57]. For the Yb(III) complex the f-f transition ( 2 F7/2 → 2 F5/2) is observed as a doublet at 941 nm and 978 nm, due to Stark splitting (Figure 1b).…”

Chemical Assembling of Heterometallic {Cd–M} (M=Li, Mg, Eu, Tb) Molecules with 3,5‐Di‐tert‐butylbenzoate Bridges and N‐Donor Ligands

“…where O 2 R is the 4-methoxybenzoate anion, L is phen, [15] or [Ln 2 Cd 2 (mbenz) 10 (phen) 2 ] (mbenz = 4-methylbenzoate anion; Ln = Nd, Pr, Sm). [17] Currently, there is only one example of a trinuclear compound containing both cadmium and lanthanide atoms [EuCd 2 (benz) 7 (phen) 2 ] (benz = benzoate anion). [16] Unlike in 3d-4f complexes with cobalt, copper, and zinc atoms, the coordination number of cadmium atoms is six and is achieved through chelate coordination of bridging carboxylate anions and coordination of small molecules such as water and ethanol.…”

“…[13] There is no information about CdÀ Ln complexes with anions of aliphatic monocarboxylic acids, but examples of compounds with aromatic carboxylate anions (benzoate, 4methylbenzoate, 4-methoxybenzoate) are known. [14][15][16][17] Using binuclear complexes [CdLn(mbenz) 5 (phen)(H 2 O)] (mbenz -the 4-methoxybenzoate anion, phen = 1,10-phenanthroline, Ln = Sm, Eu, Tb, Nd, Ho, Er) as examples, it was shown transition from lanthanide complexes to cadmium-lanthanide complexes resulted in a shift in the energy level of the triplet state of the moiety responsible for the absorption and energy transfer to the emission center, which enhanced the luminescence of complexes with the Sm(III), Eu(III) and Tb(III) ions. [15] Anions of 3,5-di-tert-butylbenzoic acid (Hbzo) have a clear advantage over benzoate anions.…”

Syntheses, structures and photophysical properties of heteronuclear Zn–Ln coordination complexes

“…can be chosen as the central metal ions of the d-block. In the recent decade, there are many reports about the luminescent properties of d-f heteronuclear coordination complexes and the selection of the central metal ions from the d-block is extensive, for example, Ru 2 þ , Os 2 þ , Cr 3 þ , Cd 2 þ , Zn 2 þ , Ag þ and so forth [29][30][31][32][33]. Among them, the Zn-Ln coordination complexes occupy an important position and most of them use Schiff-bases and their derivatives as ligands [34,35].…”