Synthesis, Structural Characterization, and Chiroptical Studies of Bidentate Salen‐Type Lanthanide (III) Complexes

Abstract

The salen-type ligand prepared with (R,R) diphenylethan-1,2-diamine and salicylaldehyde provides stable and inert complexes KLnL2 upon simple reaction with lanthanide halides or pseudohalides LnX3 (Ln = Tb(3+) -Lu(3+) ; X = Cl(-) or TfO(-) ) of its potassium salt. All the complexes were completely characterized through nuclear magnetic resonance (NMR), electronic circular dichroism (ECD) in the UV and some (Er(3+) , Tm(3+) , Yb(3+) ) also with Near-IR ECD (NIR-ECD) and luminescence (Tb(3+) , Tm(3+) ). Careful analysis of the NMR shifts demonstrated that the complexes are isostructural in solution and afforded an accurate geometry. This was further confirmed by means of Density Functional Theory (DFT) optimization of the Lu(3+) complex, and by comparing the ligand-centered experimental and time-dependent TD-DFT computed UV-ECD spectra. As final validation, we used the NIR-ECD spectrum of the Yb(3+) derivative calculated by means of Richardson's equations. The excellent match between calculated and experimental ECD spectra confirm the quality of the NMR structure.

Ab Initio Study of Circular Dichroism and Circularly Polarized Luminescence of Spin-Allowed and Spin-Forbidden Transitions: From Organic Ketones to Lanthanide Complexes

“…Theoretical work on lanthanide complexes has so far relied on CF models , in combination with the semiempirical Judd-Ofelt theory. , Recently, such CF based models were used to simulate the CD spectrum and the Raman optical activity of Ln-based compounds. TDDFT has been also used to calculate the CD spectrum of some Eu­(III) and Yb­(III) complexes, − but these studies focused on the UV–vis part of the energy spectrum which corresponds mostly to intraligand transitions.…”

“…53,54 Recently, such CF based models were used to simulate the CD spectrum 55 and the Raman optical activity 56 of Ln-based compounds. TDDFT has been also used to calculate the CD spectrum of some Eu(III) and Yb(III) complexes, [57][58][59] but these studies focused on the UV-Vis part of the energy spectrum which corresponds mostly to intra-ligand excitations. The lack of ab-initio data for the optical activity of metal-centered transitions arises from the added difficulty to take into account the effects from the spin-orbit coupling (SOC).…”

NIR‐Circularly Polarized Luminescence from Chiral Complexes of Lanthanides and d‐Metals

“…Sophisticated computational studies and low temperature measurements would be required for more in-depth assignments. [32,34,35,[65][66][67][68][69] When evaluating the NIR-CPL spectrum of Yb, it is important to discuss the balance of positive and negative signals over the entire transition. Due to Yb possessing only one intraconfigurational transition, if it can be considered decoupled from the environment (pure static coupling), one expects the integral over the entire CPL spectrum around 1000 nm to be zero.…”

Metal Salen- and Salphen-Containing Organic Polymers: Synthesis and Applications

“…Fe 2þ , 28 Fe 3þ , 29 Co 2þ , 30 Co 3þ , 31 Ni 2þ , 32 Cu 2þ , 33 Zn 2þ , 34 Ga 3þ , 35 Ge 2þ/4þ , 36 Sr 2þ , 23 Y 3þ , 37 Zr 4þ , 38 Nb 5þ , 39 Mo 4þ , 40 Tc 5þ , 41 Ru 3þ , 42 Rh 3þ , 43 Pd 2þ , 44 Ag þ , 45 Cd 2þ , 46 Sb 5þ , 47 Te 4þ , 48 La 3þ , 37 Ce 4þ , 49 Pr 3þ , 50 Nd 3þ , 51 Sm 3þ , 51 EU 3þ , 52 Gd 3þ , 51 Tb 3þ , 51 Dy 3þ , 51 Ho 3þ , 53 Er 3þ , 51 Tm 3þ , 53 Yb 3þ , 53 Lu 3þ , 53 Hf 4þ , 54 Ta 5þ , 55 W 6þ , 56 Re 4þ , 57 Os 4þ , 58 Ir 3þ , 59 Pt 2þ , 60 Au 3þ , 61 Hg 2þ , 46 Tl 3þ , 62 Bi 3þ , 63 Th 4þ , 64 U 6þ , 65 Np 5þ , 66 or Pu 4þ . 49 In contrast to metal salens, for which comparably simple chiral diamines ...…”