Electronic structures and optical properties of neutral substituted fluorene-based cyclometalated platinum(II)–acetylide complexes: A DFT exploration

Density Functional Calculation and Evaluation of the Spectroscopic Properties and Luminescent Material Application Potential of the N-Heterocyclic Platinum(II) Tetracarbene Complexes

A series of reported Pt(II) carbene complexes possibly have the ability to serve as the new generation of blue emitters in luminescent devices because of their narrow emission spectra, high photoluminescence quantum yields (PLQYs), and rigid molecular skeleton. However, the combination of all carbene ligands with different multidentate structures will affect the overall planarity and horizontal dipole ratio to varying degrees, but the specific extent of this effect has not previously been analyzed in detail. In this work, density functional computation is used to study a class of platinum tetracarbene bidentate complexes with similar absorption and emission band characteristics, which is the main reason for the remarkable difference in quantum efficiency due to subtle differences in electronic states caused by different ligands. From the calculation results, the major reason, which results in significantly decrease in quantum efficiency for [Pt(cyim)2]2+, is that [Pt(cyim)2]2+ can reach the non-radiative deactivation metal-centered d-d excited state through an easier pathway compared with [Pt(meim)2]2+. The result, based on changes in the dihedral angle between ligands, can achieve the goal of improving and designing materials by adjusting the degree of the dihedral angle. (meim: bis(1,1'-dimethyl-3,3'-methylene-diimidazoline-2,2'-diylidene); cyim: bis(1,1'-dicyclohexyl-3,3'-methylene-diimidazoline-2,2'-diylidene).

Investigate the Relationship between Structure and Triplet Potential Energy Surface to Control the Phosphorescence Quantum Yield of Platinum(II) Complex: A Theoretical Investigation

Triplet potential energy surfaces are extremely important for phosphors because they are closely related to radiative and nonradiative decay processes. In this article, the correlations between the strctures and the triplet potential energy surfaces for Pt(II) complexes are investigated in detail with the help of density functional theory (DFT). The calculated results indicate that triplet hypersurface minima with different configurations, i.e., planar and bent, rely on the geometries of the platinum(II) complex. A bent configuration could cause an obvious decrease in the phosphorescence quantum yield, and an unusual low-lying triplet excited-state decay route is proposed. In addition, the extension of π-conjugation and addition of suitable substituents, for example arylboron, are promising strategies for changing the triplet hypersurface to achieve the minimum with a planar configuration, leading to a high phosphorescence quantum yield. Moreover, to predict the triplet hypersurface, a useful and simple strategy has been put forward. In our study, the relationship between the structure and the lowest-lying triplet potential energy surface of a Pt(II) complex is constructed, which is significant and meaningful for controlling the phosphorescence quantum yield to design high-performance phosphorescent materials used in the field of organic light-emitting diodes (OLEDs).

Autotandem Catalysis: Inexpensive and Green Access to Functionalized Ketones by Intermolecular Iron-Catalyzed Amidoalkynylation/Hydration Cascade Reaction via N-Acyliminium Ion Chemistry

Iron-based catalysts were applied in cascade-type reactions for the synthesis of different carbonyl compounds. The reactions proceeded by a new iron-catalyzed cascade of alkynylation/hydration by using both the σ- and π-Lewis acid properties of iron salts. The alkynylation reactions of several endo and exocyclic acetoxylactams were achieved with three different catalysts including FeCl 3 .6H 2 O, FeCl 3 , and Fe(OTf) 3 showing the efficiency of σ-Lewis acidity of iron (III) salts in catalyzing the alkynylation reaction. We also demonstrated that the reaction sequence could be shortened by the direct use of hydroxylactams, leading to an environmentally friendly protocol, avoiding the need to perform unnecessary lengthy steps. A combination of the hard/soft iron Lewis acid properties was then used to implement an unprecedented tandem intermolecular alkynylation/intramolecular hydration sequence allowing expedient access to a new carbonyl structures from trivial materials.

Computational Studies on the Materials Combining Graphene Quantum Dots and Pt Complexes with Adjustable Luminescence Characteristics

Graphene materials with particular properties are proved to be beneficial to photoelectric devices, but there are rare reports on a positive effect by graphene on emissive layer materials of organic light-emitting diodes (OLEDs) previously. On the basis of the latest important experiments, an OLED device with the aid of graphene quantum dots shows the dawn of their application for luminescent materials. The luminescence performance has been improved, but the understanding of the internal excited-state radiation mechanism of the material needs further study. In this work, the Pt(II)-coordinated graphene quantum dot coplanar structures with different shapes are studied theoretically in detail, and the results present the improvement in phosphorescence under the promoted radiative decay and suppressed nonradiative decay. This composite combines the advantages of transition metal complexes and graphene quantum dots and also exhibits excellent properties in the light absorption region and carrier transportation for the OLED. This comprehensive theoretical calculation research can provide a comprehensive basis of the material design in the future.

Influences of donor/acceptor ratio on the optical and electrical properties of the D/A alternating model oligomers: A density functional theory study

We adopted an ingenious method that cut out the DA alternating oligomers from the corresponding DA alternating copolymers. From analyzing the orbital compositions of the HOMOs and LUMOs as well as the reorganization energies, we found the level of charge transfer is increased with the increasing of D/A ratio, but ionization potentials and electron affinities show a contrary trend. Moreover, with the greater ratio, the trend in the nearness of two transitions results in broadening the absorption band in the visible range. That is why experimentally improving the ratio is beneficial for the copolymers used as the p-type materials in the BHJ solar cells. This method is impossible to take the real copolymer system, however, it could provide a strategy to avoid the limitation of the theory level and perform reliable result to study the intrinsic properties of DA alternating copolymers, which can provide a guidance to experimental works.

The effect of the embedded o-carborane ligand on the photophysical properties of a cyclometalated Pt(ii) complex: a theoretical investigation

The embedded o-carborane ligands will have an impact on the photophysical properties and quantum efficiency of these highly efficient blue phosphorescent materials.

Density functional theory investigation on iridium(iii) complexes for efficient blue electrophosphorescence

The geometrical structures, electronic structures, optoelectronic properties and phosphorescence efficiencies of blue-emitting phosphors [Ir(fpmi)2(pyim)], [Ir(pyim)2(fpmi)], [Ir(fpmi)2(fptz)], [Ir(fpmi)2(pypz)] and [Ir(tfmppz)2(pyim)]), were investigated by DFT and TDDFT methods.

Theoretical investigation on the effect of ancillary ligand modification for highly efficient phosphorescent platinum(ii) complex design

Reasonable modification of ancillary ligands for Pt(ii) complexes can effectively improve the quantum efficiency and strengthen the rigidity of luminescent materials in organic light-emitting diodes.

The phosphorescence properties of a series of diarylethene-containing platinum complexes: the effect of ligand photoisomerization

Benefitting from isomerization in the ancillary-ligand diarylethene, a control of phosphorescence efficiency becomes available.

Dibromido(2,2':6',2''-terpyridine-κN,N',N'')zinc(II)

In the title compound, [ZnBr(2)(C(15)H(11)N(3))], the Zn(II) ion is five-coordinated by the three N atoms from a 2,2':6',2''-terpyridine ligand (terpy) and two bromide anions in a distorted trigonal bipyramidal configuration. Each mol-ecule is situated on a twofold rotational axis that passes through the Zn(II) ion and the central ring of the terpy ligand. In the crystal structure, aromatic π-π inter-actions between terpy ligands [centroid-centroid distances = 3.6265 (9) Å] link mol-ecules into stacks propagated in the [001] direction.