Near-infrared (NIR) luminescent homoleptic linear tetranuclear [Ln4((OH)2-Salophen)4] (Ln = Nd or Yb) complexes self-assembled from the dihydroxylated Salophen ligand

•Dihydroxylated Salophen-type ligand (OH)2-Salophen•Homoleptic linear tetranuclear complexes Ln4((OH)2-Salophen)4•NIR luminescent properties and energy transfer

Through self-assembly of the (OH)2-Salophen H4L (H4L = N, N′-bis(3-hydroxyl salicylidene)benzene-1,2-diamine) with LnCl3·6H2O (Ln = La, Nd, Yb, Er or Gd), series of [Ln4((OH)2-Salophen)4]-arrayed complexes [Ln4(H2L)2(L)2(EtOH)2] (Ln = La, 1; Ln = Nd, 2; Ln = Yb, 3; Ln = Er, 4 or Ln = Gd, 5) were obtained, respectively. The result of their photophysical properties shows that the strong and characteristic NIR luminescence for complexes 2–3 with emissive lifetimes in microsecond ranges is observed, and the sensitization arises from the excited state (1LC) of the (OH)2-Salophen ligand despite the luminescent quenching with OH-oscillators around the Ln3 + ions.

Graphical abstractNear-infrared (NIR) luminescent homoleptic linear tetranuclear [Ln4((OH)2-Salophen)4] (Ln = Nd or Yb) complexes self-assembled from dihydroxylated Salophen ligand (OH)2-Salophen.Figure optionsDownload full-size imageDownload as PowerPoint slide