Solid State Structures, Solution Behavior, and Luminescence of Simple Tetrakis(2‐pyridylmethyl)ethylenediamine Lanthanide Complexes

Abstract

We report the synthesis, characterization, solid‐state structure and solution behavior of simple lanthanide trifluoromethanesulfonate complexes supported by a hexadentate tetrakis(2‐pyridylmethyl)ethylenediamine ligand. The complexes' solid‐state structures exhibit different trifluoromethanesulfonate coordination, correlating with the size difference of the lanthanide ions. The ligand is capable of sensitizing Nd, Sm, Eu, Tb, Dy, and Yb yielding metal‐centered emission with moderate quantum yields.

Seven-Coordinate Tb3+ Complexes with 90% Quantum Yields: High-Performance Examples of Combined Singlet- and Triplet-to-Tb3+ Energy-Transfer Pathways

“…Thus, the considerably better photophysical performance of the chloride-containing [Tb­(bbp Y n)­Cl] ( Y = e, p) products compared with their NO 3 – analogues appears to be determined by the PBP environment of the Ln 3+ ions in the individual molecules and by their electronic structure rather than by the presence or absence of crystal chirality. This proposition on the suitability of the PBP geometry is supported by recent work by Ayers and co-workers in which the related tetrakis­(2-pyridylmethyl)­ethylenediamine (tpen) ligand generates an eight-coordinate square-antiprismatic coordination sphere for the Tb 3+ ion; the complex presents a quantum yield of 55.3% in the solid state . This value is significantly lower than those for the PBP [Tb­(bbp Y n)­Cl] ( Y = e, p; this work) and close to the result given by eight-coordinate [Tb­(bbp p n)­(NO 3 )]. , …”

“…This proposition on the suitability of the PBP geometry is supported by a recent work by Ayers and coworkers in which the related tpen ligand (tetrakis(2-pyridylmethyl)ethylenediamine) generates an eightcoordinate square-antiprismatic coordination sphere for the Tb 3+ ion; the complex presents a quantum yield of 55.3 % in the solid-state. 91 This value is significantly lower than those for PBP [Tb(bbpYn)Cl] (Y = e, p; this work) and close to the result given by eight-coordinate [Tb(bbppn)(NO 3 )]. 50,90 From the magnetic point of view, the structural differences reported above between complexes with bbpen 2− or bbppn 2− also do not significantly affect the relaxation dynamics of I and II, which are very similar.…”

Circularly Polarized Luminescence from Enantiopure C2-Symmetrical Tetrakis(2-pyridylmethyl)-1,2-diaminocyclohexane Lanthanide Complexes

“…The eight-coordinate geometry around the lanthanide can be best described as a bisdisphenoid (or dodecahedral deltahedron), where a C 2 symmetry axis crosses the vertex formed by the oxygen atoms of the trifluoromethanesulfonate ligands (Figure S45). This structure contrasts with the previously reported (tpen)­Eu­(OTf) 3 complex, which is best described as a distorted square antiprism . This slight change in geometry is possibly due to the increased rigidity of the cyclohexane backbone.…”

“…The chiral tetrakis­(2-pyridylmethyl)­diaminocyclohexane ligands (tpdac) were synthesized in a manner similar to that of the tpen ligand previously reported …”

“…In the concluding remarks of their review on lanthanide CPL, Zinna and Di Bari stated that optimum ligands for lanthanide-based CPL should (1) form a stable/inert lanthanide complex, (2) be a good sensitizer, (3) form a complex with chiral geometry that can give rise to strong CPL, and (4) form a complex with good solubility . We have recently reported that simple N , N , N ′, N ′-tetrakis­(2-pyridylmethyl)­ethylenediamine (tpen in Figure ) forms stable lanthanide complexes, exhibiting only one C 2 -symmetrical species in solution . These lanthanide complexes are modestly luminescent and soluble in polar organic solvents and lack only the ability to form a chiral geometry to potentially enable CPL.…”