Optical Properties of the Phosphorescent Trinuclear Copper(I) Complexes of Pyrazolates:  Insights from Theory

Abstract

Theoretical investigations have been performed to explore the optical properties of {[3,5-(CF3)(2)Pz]Cu}3 in monomeric and dimeric forms using TD-DFT approaches. The emission of all complexes originates from the lowest triplet excited-states (T1), and the corresponding emissive states are assigned as the mixture of the metal-centered charge transfer and ligand-to-metal charge transfer. The features of the emission spectrum are clarified in detail. The bulk emission spectrum of complex is mainly determined by the stacked dimers rather than the individual monomers. The predicted maximum emission wavelength (lambda(em)) are in good agreement with experimental values, indicating that the phosphorescence bands can be assigned to two different conformations for the neighboring stacked dimers sharing the same monomer in the complex. Energy transfer from T1 of one stacked dimer to the neighboring one is responsible for the disappearance of the shoulder, leaving only the main peak upon heating. With the aim to reveal the conformational dependence for the triplet excited-state emission spectrum, the optical properties of various stacked dimers with different conformations are investigated by varying the relative arrangements through changing inter-monomer distance or rotational angles for the dimer which is responsible for the main peak emission. Calculation results suggest that the shortest intermolecular Cu...Cu distance plays an important role in the emission spectra of the vertical- and tilting-movement dimers, which is ascribed to the variation of the energy gap for the frontier molecular orbitals involved in the main emitting transition. The blue shift of lambda(em) in parallel-movement and rotational dimers can be traced back to the variation of the mutual spatial orientation. Therefore, the modulation of the extent of movement or rotational angles for stacked dimers by external perturbations creates new possibilities for the design of molecular light-emitting devices.

Supramolecular Phosphorescent Trinuclear Copper(I) Pyrazolate Complexes for Vapochromic Chemosensors of Ethanol

“…Molecular geometry and optical properties of luminescent d 10 complexes have been found to show the characteristic of chemosensors in particular applications [22]. For example, trinuclear metal pyrazolate complexes with different from their substituents and metals on ligands have been reported to show interesting bright and tunable luminescence properties [23].…”

“…6f, green dot). Such quenching of intensity in 100% indicates that the chairlike coordination geometry of Cu(I)-Cu(I) metallophilic interaction [4,[19][20][21][22][23][24][25][26][27]35] was totally disrupted through the columnar assembly of the weak intermolecular interaction. In this case, Cu(I) ions in one pyrazole ring are unable to form metal-metal interaction with other Cu(I) ions of the ligand.…”

Can DFT methods correctly and efficiently predict the coordination number of copper(I) complexes? A case study

“…19 Additional studies utilized the LAND2DZ basis set -RECP (relativistic effective core potential) combination, 20,21 or combined LANL2DZ for copper with the 6-31G* basis set for other atoms. [22][23][24][25] These studies, again, focused on geometrical aspects which were found to be sometimes exaggerated by the calculations. 22 Some of these studies sought to understand the relation between both the geometry and the electronic structure on the one hand, and different spectra of various copper complexes on the other hand.…”

“…22 Some of these studies sought to understand the relation between both the geometry and the electronic structure on the one hand, and different spectra of various copper complexes on the other hand. 23,24 Other studies tried to predict, based on the geometric preference of the complex, whether the ligands involved would actually bind copper 25 or attempted to determine the chemical softness/hardness of copper(I) based on trends in the heat of formation of copper with various ligands. 22 All these studies, however, due to the relatively low level of theory, dealt mainly with structure and electronic properties, rather than coordination number and absolute energies.…”

Push-pull effect on the geometrical, optical and charge transfer properties of disubstituted derivatives of mer-tris(4-hydroxy-1,5-naphthyridinato) aluminum (mer-AlND3)

“…Frequency calculations have been carried out to ensure that the optimized geometry has all positive frequencies and thus is a minimum on the potential energy surface. The first excited state (S 1 ) geometries have been optimized using the ab initio CIS approach [37] and previously this approach has been applied on mer-Alq3 and its derivatives [54][55][56][57][58][59][60][61][62][63], mer-AlND3 and its methyl derivatives [64] and other OLED materials [67][68][69][70][71] which has given reliable results. The absorption and emission spectra of these derivatives have been evaluated at by PBE0/6-31G(D) method using the B3LYP/6-31G(D) and CIS/6-31G(D) optimized geometries respectively.…”