HOMO Of Complexes Research Articles

Theoretical exploration of the electronic structure and photophysical properties of five cyclometalated Ir(III) complexes bearing different substituted acetylacetone moieties

Using time-dependent density functional theory (TDDFT) approach, the electronic structure and photophysical properties of five cyclometalated Ir(III) complexes bearing different substituted acetylacetone moieties have been calculated and investigated. The calculated geometry structure of complex 2 shows a very good agreement with the available experimental data. The HOMO of complex 1 has the different distribution from those of complexes 2–5, that is, residing on the d-orbital of Ir, π-orbital of acac and L ligands. The S0 → S1 transition of complex 1 is from HOMO → LUMO and HOMO–1 → LUMO, that is, different from those of complexes 2–5. The lowest energy emissions for these complexes from CAM-B3LYP level are localized at 591, 581, 576, 574, and 571, respectively. Complex 4 might possess the largest kr value among these studied complexes. We anticipate that this study can shine some light on Ir(III) emitters in the fabrication of efficient organic light-emitting diodes (OLEDs).

Synthesis, structural characterization and biological properties of cyclometalated iridium(III) complexes containing 2-methyl-3-{(E)-[(quinolin-2-yl)methylidene]amino}quinazolin-4(3H)-one

Two Iridium(III) complexes [Ir(ppy)2((mqmaq)]+ (1) and [Ir(bhq)2((mqmaq)]+ (2) {ppy = 2-phenylpyridine, bhq = benzo[h]quinoline, mqmaq = 2-methyl-3-{(E)-[(quinolin-2-yl)methylidene]amino}quinazolin-4(3H)-one} have been designed, synthesized and structurally characterized. Complex 2 has been structurally characterized by single-crystal X-ray structure determination. The experimentally obtained results of photophysical properties of complexes 1 and 2 well agree with the theoretically calculated results acquired by density functional theory (DFT) studies. The HOMO of complexes 1 and 2 are delimited on the iridium and cyclometalated aromatic ligands, while LUMO, is localized on quinoline-based mqmaq ligand whereas LUMO + 1, and LUMO + 2 are primarily restricted on cyclometalated ligands. The interaction of complexes with calf thymus DNA (CT-DNA) was investigated by absorption titration and emission titration experiments. Furthermore, the cytotoxicity and cellular localization properties of these complexes towards HeLa cells have been investigated.

Hemi Labile Intramolecular N → Sn Coordination in a Diorganotin (IV) Sulfide [R2Sn(µ-S)]2 (R = 2-phenylazophenyl) Complex: Synthesis, Structure, DFT-NBO and Antibacterial Studies

The dinuclear diorganotin sulfide [R2Sn(µ-S)]2 (1) (R = 2-phenylazophenyl) was synthesized by the room temperature reaction of the N → Sn intramolecularly coordinated starting precursor R2SnCl2 and Na2S·9H2O in acetone/methanol (1:1). The molecular structure of 1 was primarily characterized by single crystal X-ray crystallography. Furthermore, 1 was also characterized by other experimental techniques, such as 1H, 13C and 119Sn NMR, ESI-MS, FTIR spectroscopy. Complex 1 crystallized in the monoclinic P21/n space group. Each tin center of complex 1 is pentacoordinated and acquires a distorted trigonal bipyramidal geometry. Time dependent density functional theory (TD-DFT) analysis revealed that the transitions observed in complex 1 are predominantly of the ligand-to-ligand type. Natural bond orbital (NBO) analysis showed that complex 1 consists of three ionic bonds (2Sn-C and Sn-S) and two ligand to metal coordinate bonds (S → Sn and N → Sn). HOMO-LUMO analysis suggested that the HOMO of complex 1 is mainly sulfur based. The complex 1 showed significant bactericidal activity against both gram positive and negative bacteria.

Wirelike dinuclear ruthenium(II)polyterpyridine complexes based on D–P–A architecture: Experimental and theoretical investigation

Abstract To accomplish the goal of prolonged excited state, efficient for interfacial electron injection and low electron-hole recombination (LUMO → HOMO of complex) we have synthesized a heteroleptic complexes 1 and 2 based on D–P–A architecture (where P = Photosensitizer, A = Acceptor and D = Donor). The complexes 1 and 2 show the average excited state lifetimes (τavg) of 25 ns and 12.67 ns respectively compared to 0.25 ns for [Ru(tpy)2]2PF6. The τavg of such an order is sufficient for performing the interfacial electron transfer into the conduction band of TiO2 and redox chemistry of excited state. The electrochemical studies exhibit the oxidation potential (Eox) of 1.23 V and 1.27 V vs SCE with associated excited-state redox potentials ( E o x * = − 0.95 V and −0.85 V and E r e d * = 1.0 V and 0.88 V for complexes 1 and 2 respectively) have evidence for stronger reductant and oxidant behaviour in 1MLCT excited state. Subsequent interfacial study with TiO2 nanocrystal is in good agreement with photo induced electron injection from LUMO of complex to conduction band (CB) of TiO2 as LUMO level (−3.22 eV and 3.16 eV for complexes 1 and 2 respectively) of complexes is above the CB of TiO2 (−3.65 eV). The experimental photophysical results of both the complexes are well supported by time dependent density functional theory.