Understanding adsorption geometry of organometallic molecules on graphite

To comprehensively investigate the adsorption geometries of organometallic molecules on graphene, Cp*Ru+ fragments as an organometallic molecule is bound on highly oriented pyrolytic graphite and imaged at atomic resolution using scanning tunneling microscopy (STM) (Cp* = pentamethylcyclopentadienyl). Atomic resolution imaging through STM shows that the Cp*Ru+ fragments are localized above the hollow position of the hexagonal structure, and that the first graphene layer adsorbed with the fragments on the graphite redeveloped morphologically to minimize its geometric energy. For a better understanding of the adsorption site and molecular geometry, experimental results are compared with computed calculations for the graphene surface with Cp*Ru+ fragments. These calculations show the adsorption geometries of the fragment on the graphene surface and the relationship between the geometric energy and molecular configuration. Our results provide the chemical anchoring geometry of molecules on the graphene surface, thereby imparting the theoretical background necessary for controlling the various properties of graphene in the future.

Understanding Adsorption Geometry of Organometallic Molecules on Graphene

To comprehensively investigate the adsorption geometries and behaviors of organometallic molecules on graphene, Cp*Ru+ fragments as an organometallic molecule is bound on highly oriented pyrolytic graphite and imaged at atomic resolution using scanning tunneling microscopy (STM) (Cp* = pentamethylcyclopentadienyl). Atomic resolution imaging through STM shows that the Cp*Ru+ fragments are localized above the hollow position of the hexagonal structure, and that the graphene surface adsorbed with the fragments redeveloped morphologically to minimize its geometric energy. For a better understanding of the adsorption site and molecular geometry, experimental results are compared with computed calculations for the graphene surface with Cp*Ru+ fragments. These calculations show the adsorption geometries of the fragment on the graphene surface and the relationship between the geometric energy and molecular configuration. Our results provide the chemical anchoring geometry of molecules on the graphene surface, thereby imparting the theoretical background necessary for controlling the electrical/physical properties of graphene in the future.

Emerging Molecular Receptors for the Specific-Target Delivery of Ruthenium and Gold Complexes into Cancer Cells

Cisplatin and derivatives are highly effective in the treatment of a wide range of cancer types; however, these metallodrugs display low selectivity, leading to severe side effects. Additionally, their administration often results in the development of chemoresistance, which ultimately results in therapeutic failure. This scenario triggered the study of other transition metals with innovative pharmacological profiles as alternatives to platinum, ruthenium- (e.g., KP1339 and NAMI-A) and gold-based (e.g., Auranofin) complexes being among the most advanced in terms of clinical evaluation. Concerning the importance of improving the in vivo selectivity of metal complexes and the current relevance of ruthenium and gold metals, this review article aims to survey the main research efforts made in the past few years toward the design and biological evaluation of target-specific ruthenium and gold complexes. Herein, we give an overview of the inorganic and organometallic molecules conjugated to different biomolecules for targeting membrane proteins, namely cell adhesion molecules, G-protein coupled receptors, and growth factor receptors. Complexes that recognize the progesterone receptors or other targets involved in metabolic pathways such as glucose transporters are discussed as well. Finally, we describe some complexes aimed at recognizing cell organelles or compartments, mitochondria being the most explored. The few complexes addressing targeted gene therapy are also presented and discussed.

Theoretical study of new push–pull molecules based on transition metals for NLO applications and determination of ICT mechanisms by DFT calculations

This study is based on the valuation of a few model molecules. The objective of this research is focussed on the nonlinear optical (NLO) improvement of four organometallic molecules and one organic molecule. These molecules have been subjected to several calculations by different functionals: CAM–B3LYP, LC–BLYP, LC–wPBE, wB97X, M11, M06–2X, M08–HX and M08–SO. These functionals gave three orders of classification of the [Formula: see text] parameters. The CAM–B3LYP functional recorded very good agreement between [Formula: see text] parameters and gaps ([Formula: see text]. Significant first hyperpolarizabilities ([Formula: see text] have been obtained around 880 * 10[Formula: see text][Formula: see text]esu. The mechanisms of intramolecular charge transfer (ICT) have shown energetic passages from donor groups to acceptors and vice versa. The substitution of metals influences the location of [Formula: see text] electrons at the level of the chromophores. Finally, the lengthening of the aromatic chains between the acceptor and donor groups shows significant NLO improvements. The first and second hyperpolarizabilities ([Formula: see text] and ([Formula: see text] for a chain of several benzene rings are of the order of 21,663.16 * 10[Formula: see text][Formula: see text]esu and 16,464.65 * 10[Formula: see text][Formula: see text]esu, respectively.

Tunable Magnetism of Organometallic Nanoclusters by Graphene Oxide On-Surface Chemistry

Assembly of interacting molecular spins is an attractive candidate for spintronic and quantum computing devices. Here, we report on-surface chemical assembly of aminoferrocene molecules on a graphene oxide (GO) sheet and their magnetic properties. On the GO surface, organometallic molecules having individual spins through charge transfer between the molecule and the sheet are arranged in nanoclusters having diameters of about 2 nm. The synthetic fine tuning of the reaction time enables to change the interspacing between the nanoclusters, keeping their size intact. Their magnetism changes from paramagnetic behavior to collective one gradually as the interspacing decreases. The creation of collective nature among weakly interacting molecular spins through their nanoscale arrangement on the GO surface opens a new avenue to molecular magnetism.

Mechanistic Study of Nucleation Enhancement in Atomic Layer Deposition by Pre-Treatment with Small Organometallic Molecules

<p>Thermal atomic layer deposition (ALD) of metals on metal oxide surfaces typically suffers from nucleation delays that result in poor-quality films. The poor nucleation may be caused by a lack of suitable chemisorption sites on the oxide surface which are needed for metal nucleation to occur. In this work, we demonstrate that pre-functionalizing the surface with a sub-monolayer of small organometallic molecules from the vapor phase can lead to a significant increase in surface coverage of the metal deposited by ALD. This process is demonstrated for Pt ALD from (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe₃) and O₂, with nucleation enhanced almost three-fold at 100 ALD cycles after the pre-treatment, and even more significantly at lower ALD cycle numbers. We hypothesize that the high coverage of the organometallic molecule provides an alternative chemisorption mechanism for the platinum precursor and thus leads to an increase in nucleation sites. The growth of the platinum deposits was investigated in depth though scanning electron microscopy (SEM) and grazing incidence small angle x-ray scattering (GISAXS). These studies show that the pre-treatment results in the growth of larger and more highly ordered Pt nanoparticles at early cycle numbers, which subsequently coalesce into continuous and pinhole free films. Surface pretreatment by organometallic molecules therefore introduces a potential route to achieve improved nucleation and growth of ultrathin films.</p>

Mechanistic Study of Nucleation Enhancement in Atomic Layer Deposition by Pre-Treatment with Small Organometallic Molecules

<p>Thermal atomic layer deposition (ALD) of metals on metal oxide surfaces typically suffers from nucleation delays that result in poor-quality films. The poor nucleation may be caused by a lack of suitable chemisorption sites on the oxide surface which are needed for metal nucleation to occur. In this work, we demonstrate that pre-functionalizing the surface with a sub-monolayer of small organometallic molecules from the vapor phase can lead to a significant increase in surface coverage of the metal deposited by ALD. This process is demonstrated for Pt ALD from (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe₃) and O₂, with nucleation enhanced almost three-fold at 100 ALD cycles after the pre-treatment, and even more significantly at lower ALD cycle numbers. We hypothesize that the high coverage of the organometallic molecule provides an alternative chemisorption mechanism for the platinum precursor and thus leads to an increase in nucleation sites. The growth of the platinum deposits was investigated in depth though scanning electron microscopy (SEM) and grazing incidence small angle x-ray scattering (GISAXS). These studies show that the pre-treatment results in the growth of larger and more highly ordered Pt nanoparticles at early cycle numbers, which subsequently coalesce into continuous and pinhole free films. Surface pretreatment by organometallic molecules therefore introduces a potential route to achieve improved nucleation and growth of ultrathin films.</p>

Enhancing Nucleation in Atomic Layer Deposition by Pre-Treatment with Small Organometallic Molecules

<p>Thermal atomic layer deposition (ALD) of metals on metal oxide surfaces typically suffers from nucleation delays that result in poor-quality films. The poor nucleation may be caused by a lack of suitable chemisorption sites on the oxide surface which are needed for metal nucleation to occur. In this work, we demonstrate that pre-functionalizing the surface with a sub-monolayer of small organometallic molecules from the vapor phase can lead to a significant increase in surface coverage of the metal deposited by ALD. This process is demonstrated for Pt ALD from (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe₃) and O₂, with nucleation enhanced almost three-fold at 100 ALD cycles after the pre-treatment, and even more significantly at lower ALD cycle numbers. We hypothesize that the high coverage of the organometallic molecule provides an alternative chemisorption mechanism for the platinum precursor and thus leads to an increase in nucleation sites. The growth of the platinum deposits was investigated in depth though scanning electron microscopy (SEM) and grazing incidence small angle x-ray scattering (GISAXS). These studies show that the pre-treatment results in the growth of larger and more highly ordered Pt nanoparticles at early cycle numbers, which subsequently coalesce into continuous and pinhole free films. Surface pretreatment by organometallic molecules therefore introduces a potential route to achieve improved nucleation and growth of ultrathin films.</p>