Quantum Chemical Studies On Luminescent Properties Of Several Typical Au(I)-Conjugated Systems

We study the electronic structures and spectroscopic properties of the excited states of several typical Au(I)-conjugated systems by ab initio methods. Ground state and excited state electronic structures are calculated by MP2 methods with electron correlation and CIS methods, respectively. The electron spectroscopic theory of vertical transition method indicates that the excited states calculated by the configuration interaction(CI) methods correspond to the vertical absorption of the system with the geometry structures of the ground states unchanged. Presumed that the ground states of the system are singlet state, the transition spectra from excited states to ground states correspond to the phosphorescence of the system with the stable geometry structures of the excited triplet states unchanged. We calculate the excited states and spectra by the single excitation configuration interaction(CIS) methods. By analyzing the composition, symmetry, electronic distribution of the molecular orbitals and the gross orbital populations calculated for the ground states and excited states, we obtain the transition properties of the molecular orbitals and the electronic transition properties. Comparing the natures of the Au(I) complexes with the properties of the corresponding compounds made of aryl or alkynyl, we find Au(I)effect is important and clear in complexes. Main results following:1. The luminescence of H3PAu(C=C)nAuPH3(n=l~6) has been studied by ab initio. The structures of the Au complexes are fully optimized by the MP2 method for the ground states and the CIS method for the excited states. In the ground states, it is clear that the molecule distances shorten to middle; Au(I) effect weakens bonds inside ligand; In the triplet excited states, the bonds of metal and ligand weaken because of electron transitions, which becomes clear with the molecules being long. The lowest-energy phosphorescences of the binear Au(I) complexes, which have the nature of Au(6p) and p(C = C) Au(5d) and p (C = C), are attributed to Au ligand charge transfer (MLCT), accompanied by Au(6p)Au(5d) transition character(MCCT) and -PH3 C transition character(LLCT). We find that difference of electronic transition decreases with ligand augmenting that the lowest-energy phosphorescence wavelengthe increases with ligand augmenting. We forecast that the lowest-energy phosphorescence of H3PAu(C=C) AuPH3 is 10833.3 cm"1. The Au(I) effect makes distributing and transitions of charge disciplinary and the electronic transitions active, which can produce better luminescent properties of materials.2. The structures of H3PAuC=CPh(a), H3PAu(C=C-l,4-C6H4)Ph(b) and H3PAu(C=C-l,4-C6H4)C=CPh(c) are optimized by the abinitio MP2 and CIS methods for the ground states and excited states respectively to study the luminescent mechanism for Au(I) complexes. Calculation indicates that the Au—C and P—Au of excited states of Au(I) complexes are longer than these of groud states, which testifies electron transitions make the bonds betweenAu and ligand weak. The lowest-energy phosphorescences of Au(I) complexes arising from A3A'-^'A' are 530.0nm of a, 610.2nm of b and 604.8nm of c, respectively, which are all consistent experimental data. The lowest-energy phosphorescences of Au(I) complexes, which are attributed to Au—?ligand charge transfer(MLCT), accompanied by Au(6p)—>Au(5d)transition character(MCCT), have the nature of p,*(—C=C— ^=C —, -0") with Au(l) effect. Moreover, Au(I) effect for phosphorescences ofAu(I) complexes decreases with ligand increasing.3. The luminescence of the l,4-bi(AuPH3-C=C)-C6H4(a) and (AuPH3-C= C)2(l,4-C6H4)2(b) complexes are studied by ab initio methods. The structures of the binear Au(I) complexes are fully optimized by the MP2 method for the ground states and the CIS method for the excited states. The 45.0° dihedral angel of two phenyl planes of ' A ground state of b is ascribed to some degree of pjt bond between two phenyls, which is showed by spatial plot of the highest occupied molecular orbital. However, two phenyls of the 3B excited state of b are nearly coplanar, which is by reason of the full pK bond between two phenyls. The lowest-energy phosphorescences are calculated at 609.3nm for a arising from ^.-^Ag and 614.8nm for b arising from 3B-*'A. The lowest-energy phosphorescences of the binear Au(I) complexes, which havethe nature of p,*(-C=C- > -?-)-~p?(-C=C-, -?-) with Au(I) effect, are attributed to Au-^ligand charge transfer(MLCT), accompanied by Au(6p)->Au(5d) transition character(MCCT). The Au(I) effect makes the transitions of molecular orbitals active, which can produce better luminescent...