Luminescent Eu(III) and Gd(III) Trisbipyridine Cryptates: Experimental and Theoretical Study of the Substituent Effects

Abstract

Synthesis, absorption spectra and luminescebce properties of a series of lanthanide trisbipyridine cryptates Ln within R-Bpy x R-Bpy x R-Bpy, where Ln = Eu, Gd and R = H, COOH, COOCH3, CONH(CH2)2NH2 are described. Comparison of the unsubstituted parent compound with the substituted compounds shows that bipyridine substitution doesn't alter significantly the photophysical properties of the lanthanide cryptate. The absorption maximum is slightly red-shifted when three bipyridines are substituted, whereas substituting one bipyridines has a negligible effect on the absorption spectra. The experimental triplet state energy is between 21600 and 22 100 cm(-1) for the series of compounds and the luminescence lifetimes at 77 K are between 0.5 and 0.8 ms in HO2 and equal to 1.7 ms in D2O. The experimental characterizations are completed by DFT and TD-DFT calculations to assess the ability of these approaches to predict absorption maxima, triplet state energies and structural parameters of lanthanide cryptates and to characterize the electronic structure of the excited states. The calculations on the unsubstituted parent and substituted compounds show that absorption maxima and lowest 3pipi* triplet state energies can be accurately determined from density functional theory (DFT) and time-dependent (TD) DFT calculations.

Applications of Density Functional Theory (DFT) to Investigate the Structural, Spectroscopic and Magnetic Properties of Lanthanide(III) Complexes

“…Following the work of Picard [241], other authors employed succesfully B3LYP and TD-B3LYP calculations, in combination with large-core RECPs, to investigate different lanthanide complexes. For instance, this approach was used to investigate the absorption spectra of different Eu III and Gd III trisbipyridine cryptates [243]. TDDFT calculations provided absorption spectra for these complexes in nice agreement with the experiment.…”

The role of ligand to metal charge-transfer states on the luminescence of Europium complexes with 18-membered macrocyclic ligands

“…For this purpose the triplet states were optimized at the TPSSh/LCRECP/6-31G(d,p) level and their energies with respect to the singlet ground state were obtained (∆SCF method). 34 Thus, the energies of the lowest-energy excited triplet states include the relaxation effects in the triplet excited states. The results (Table 4) indicate that the energies of the lowestenergy 3 ππ* states of [EuL 1 ] 3+ and [EuL 2 ] 3+ are virtually identical (∼28 610 cm -1 ).…”

Conformational effects, molecular orbitals, and reaction activities of bis(phthalocyaninato) lanthanum double-deckers: Density functional theory calculations

“…29 In recent years, density functional theory (DFT) of hybrid B3LYP functional with Becke exchange 34 and Lee-Yang-Parr correlation 35 has been proved suitable for calculating the energy-minimized structure, electronic distribution, molecular orbitals, infrared (IR) spectrum, electronic transfer, and electronic absorption spectra of a series of lanthanide-organic complexes. [36][37][38][39][40][41][42] As far as the electronic structures of lanthanide-organic complexes are concerned, a type of mixed basis set obtained by combination of triple-zeta Stuttgart RSC Segment/ECP basis set (RECP) 43,44 for lanthanide and triple-zeta split-valence Pople basis sets for short-period elements was considered as a more accurate description than the mixture of double-zeta LanL2DZ for lanthanide and double-zeta split-valence Pople basis sets for short-period elements. [45][46][47][48] In addition, the Fukui function, defined as the derivative of the electron density with respect to the total number of electrons in the system, has been taken as the common descriptor of reactive activity of the corresponding system.…”

“…[18][19][20]50,51 A type of mixed basis set, relativistic effective core potentials (RECP) 43,44 for lanthanide and Pople basis sets for short-period elements, is also proved suitable for the lanthanide-organic complexes. [37][38][39][40]45,50 In the present case, B3LYP 34,35 was used to study the molecular structure and electronic structure of the bis(phthalocyaninato) lanthanum complex in the neutral, positive mono-cation, and negative mono-anion form. The 6-311++G(2df,2pd)// 6-311+G(d,p) basis set was used for C, N, and H atoms.…”