Comparison Between Binuclear and Mononuclear Ru(II) Complexes: Synthesis, Structure, Photophysics, and Oxygen Sensing Performance

Owing to their attractive potential in optoelectronic application, luminescent Ru(II) complexes with diamine ligands are harvesting more and more research efforts. These literature efforts, however, are mostly mononuclear ones, with no detailed discussion on the performance comparison between mononuclear and multinuclear Ru(II) complexes. This work synthesized three diamine ligands having two or multiple chelating sites in each ligand, as well as their Ru(II) complexes. The single-crystal structure, electronic structure, and photophysical parameters of these Ru(II) complexes were analyzed and compared. It was found that multinuclear Ru(II) complexes had a pure MLCT (metal-to-ligand charge transfer)–based emissive center, showing longer emission lifetime and higher emission quantum yield, which were desired for oxygen sensing. Then, the oxygen sensing performance of these mononuclear and multinuclear Ru(II) complexes was systematically compared by doping them into polymer fibers via electrospinning method. Improved oxygen sensing performance was observed from binuclear Ru(II)-doped nanofibrous samples, compared with the sensing performance of mononuclear ones, including higher sensitivity, shorter response/recovery time, and better photostability. The causation was attributed to the fact that the emissive state of multinuclear Ru(II) complexes was MLCT-based ones and thus more sensitive to O2 quenching than monocular Ru(II) complexes whose emissive state was a mixture of MLCT and LLCT (ligand-to-ligand charge transfer). In addition, a multinuclear Ru(II) complex had multiple emissive/sensing components, so that its sensing collision probability with O2 was increased, showing better photostability and shorter response/recovery time. The novelty of this work was the linear oxygen sensing curve, which was rarely reported in the previous work.

The Early Steps of Molecule-to-Material Conversion in Chemical Vapor Deposition (CVD): A Case Study

Transition metal complexes with β-diketonate and diamine ligands are valuable precursors for the chemical vapor deposition (CVD) of metal oxide nanomaterials, but the metal-ligand bond dissociation mechanism on the growth surface is not clarified yet. We address this question by Density Functional Theory (DFT) and <i>ab initio</i> molecular dynamics (AIMD) in combination with the Bluemoon (BM) statistical sampling approach. AIMD simulations of the Zn β-diketonate-diamine complex Zn(hfa)₂TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = <i>N</i>,<i>N</i>,<i>N’</i>,<i>N’</i>-tetramethylethylenediamine) show that rolling diffusion of this precursor at 500 K on a hydroxylated silica slab leads to an octahedral-to-square pyramidal rearrangement of its molecular geometry. The free energy profile of the octahedral-to-square pyramidal conversion indicates that the process barrier (5.8 kcal/mol) is of the order of magnitude of the thermal energy at the operating temperature. The formation of hydrogen bonds with surface hydroxyls plays a key role in aiding the dissociation of a Zn-O bond. In the square-pyramidal complex, the Zn center has a free coordination position, which might promote the interaction with incoming reagents on the deposition surface. These results provide a valuable atomistic insight on the molecule-to-material conversion process which, in perspective, might help to tailor by design the first nucleation stages of the target ZnO-based nanostructures.<br>

The Early Steps of Molecule-to-Material Conversion in Chemical Vapor Deposition (CVD): A Case Study

<p>Transition metal complexes with β-diketonate and diamine ligands are valuable precursors for the chemical vapor deposition (CVD) of metal oxide nanomaterials, but the metal-ligand bond cleavage mechanism on the growth surface is not clarified yet. We address this question by Density Functional Theory (DFT) and <i>ab initio</i> molecular dynamics (AIMD) in combination with the Bluemoon (BM) statistical sampling approach. AIMD simulations of the Zn β-diketonate-diamine complex Zn(hfa)₂TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = <i>N</i>,<i>N</i>,<i>N’</i>,<i>N’</i>-tetramethylethylenediamine) show that rolling diffusion of this precursor at 500 K on a hydroxylated silica slab leads to an octahedral-to-square pyramidal rearrangement of its molecular geometry. The free energy profile of the octahedral-to-square pyramidal conversion indicates that the process barrier (5.8 kcal/mol) is of the order of the thermal energy at the operating temperature. The formation of hydrogen bonds with surface hydroxyls plays a key role in aiding the cleavage of a Zn-O bond. In the square-pyramidal complex, the Zn center has a free coordination position, which might promote the interaction with incoming reagents on the deposition surface. These results provide a valuable atomistic insight on the molecule-to-material conversion process which, in perspective, might help to tailor by design the first nucleation stages of the target ZnO-based nanostructures.<b></b></p>

The Early Steps of Molecule-to-Material Conversion in Chemical Vapor Deposition (CVD): A Case Study

<p>Transition metal complexes with β-diketonate and diamine ligands are valuable precursors for the chemical vapor deposition (CVD) of metal oxide nanomaterials, but the metal-ligand bond cleavage mechanism on the growth surface is not clarified yet. We address this question by Density Functional Theory (DFT) and <i>ab initio</i> molecular dynamics (AIMD) in combination with the Bluemoon (BM) statistical sampling approach. AIMD simulations of the Zn β-diketonate-diamine complex Zn(hfa)₂TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = <i>N</i>,<i>N</i>,<i>N’</i>,<i>N’</i>-tetramethylethylenediamine) show that rolling diffusion of this precursor at 500 K on a hydroxylated silica slab leads to an octahedral-to-square pyramidal rearrangement of its molecular geometry. The free energy profile of the octahedral-to-square pyramidal conversion indicates that the process barrier (5.8 kcal/mol) is of the order of the thermal energy at the operating temperature. The formation of hydrogen bonds with surface hydroxyls plays a key role in aiding the cleavage of a Zn-O bond. In the square-pyramidal complex, the Zn center has a free coordination position, which might promote the interaction with incoming reagents on the deposition surface. These results provide a valuable atomistic insight on the molecule-to-material conversion process which, in perspective, might help to tailor by design the first nucleation stages of the target ZnO-based nanostructures.<b></b></p>

Current Development of Metal Complexes with Diamine Ligands as Potential Anticancer Agents

Background:: The discovery of cisplatin and the subsequent research revealed the importance of dinitrogen-containing moiety for the anticancer action of metal complexes. Moreover, certain diamine ligands alone display cytotoxicity that contributes to the overall activity of corresponding complexes. Objective:: To summarize the current knowledge on the anticancer efficacy, selectivity, and the mechanisms of action of metal complexes with various types of diamine ligands. Method:: The contribution of aliphatic acyclic, aliphatic cyclic, and aromatic diamine ligands to the anticancer activity and selectivity/toxicity of metal complexes with different metal ions were analyzed by comparison with organic ligand alone and/or conventional platinum-based chemotherapeutics. Results:: The aliphatic acyclic diamine ligands are present mostly in complexes with platinum. Aliphatic cyclic diamines are part of Pt(II), Ru(II) and Au(III) complexes, while aromatic diamine ligands are found in Pt(II), Ru(II), Pd(II) and Ir(III) complexes. The type and oxidation state of metal ions greatly influences the cytotoxicity of metal complexes with aliphatic acyclic diamine ligands. Lipophilicity of organic ligands, dependent on alkyl-side chain length and structure, determines their cellular uptake, with edda and eddp/eddip ligands being most useful in this regard. Aliphatic cyclic diamine ligands improved the activity/toxicity ratio of oxaliplatin-type complexes. The complexes with aromatic diamine ligands remain unexplored regarding their anticancer mechanism. The investigated complexes mainly caused apoptotic or necrotic cell death. Conclusion:: Metal complexes with diamine ligands are promising candidates for efficient and more selective alternatives to conventional platinum-based chemotherapeutics. Further research is required to reveal the chemico-physical properties and molecular mechanisms underlying their biological activity.

Dicopper(ii) tetrapyridyl complexes incorporated with ancillary ligands for effective water oxidation

Water oxidation catalysis of dicopper(ii) tetrapyridyl complexes under alkaline conditions was improved by diamine ligands.

Self-assembly of an organometallic Fe9O6 cluster from aerobic oxidation of (tmeda)Fe(CH2tBu)2

Aerobic oxidation of (tmeda)Fe(CH2tBu)2 in toluene or THF solution leads to the self-assembly of a magic-sized all-ferrous oxide cluster containing the Fe9O6 subunit and bearing organometallic and diamine ligands.