Complexes of carbene-functionalized diamondoids and metal atoms: Electronic properties
Graphical abstract
Introduction
Nano-sized hydrogen terminated diamondoids can assume various sizes and chemical modifications and can be found in petroleum [1], [2]. The diamondoids can also be selectively synthesized in the laboratory [3] or nucleated from energetic species [4]. These nanostructures have shown a high potential to be used in nanotechnology, from drugs to field emitting devices [5], [6], [7], [8]. The first and smallest member of the diamondoid family is known as adamantane (C10H16). These nano-diamond cages can attach on metallic surfaces through a thiol group [9], [10] and form self-assembled monolayers (SAMs) with a negative electron affinity [5], [11] and a strong monochromatic emission [5], [12]. Such properties make diamondoids very promising candidates for electronics applications especially electron emitting devices. In the past, thiol based SAMs on metal surfaces have led to significant applications in the field of surface emission, sensing, electrochemistry, drug delivery, and microelectronics [13], [14], [15], [16], [17]. Nevertheless, the thermal instability of these thiol-based diamondoid SAMs on gold is questionable. There have been indications, that changes in the environmental conditions have a strong effect on these materials and their use for industrial purposes could be problematic [18], [19], [20], [21], [22]. Thiol-based SAMs are found to be stable only when stored in an ultra high vacuum in the absence of light, but tend to degrade after few weeks at room temperature [23], [24], [25].
As an alternative to thiol, carbene molecules have recently been used to promote binding of diamondoids on metal surfaces [26]. These molecules belong to the family of N-heterocyclic carbenes to which we refer to in the following. Carbene molecules (R-(C:)-R′ or R = C:) are usually defined as neutral compounds having a divalent carbon atom with a six-electron valence shell and are powerful tools in organic chemistry having numerous applications in chemical processes [27]. Various classes of carbene molecules can be synthesized using different methods [28] and most commonly contain at least one nitrogen atom within the ring structure [29]. N-heterocyclic carbenes (e.g. (R2N)2C:, where the ‘R’s are typically alkyl and aryl groups) are typically used as ligands for transition metals, upon coordination to p-block elements and as organocatalysts and are used in relevant applications in important catalytic transformations in the chemical industry and as organocatalysts. The reactivity of carbene molecules upon coordination to main group elements is an additional important property in view of applications. Imidazolylidene (C3N2H6), a simple ring structure with two nitrogen atoms is one member of the carbene family. This molecule can form metal and transition metal complexes [30], [31] to be used in catalysis and other chemical reactions.
In this work, we study the structural and electronic properties of imidazolylidene-functionalized diamondoids and their bonding and interaction to metal atoms. In the following sections, we present the methodology of our investigation and move on to the analysis of the results on the structural and electronic properties of carbene-functionalized diamondoids, their thermal stability, and the characteristics on their interactions with metals.
Section snippets
Methodology
This work is carried out within the density-functional-theory (DFT) based approach implemented in the code SIESTA [32], in which the Kohn-Sham eigenstates are expanded using a linear combination of atomic orbitals. The Perdew-Berke-Ernzerhof (PBE) general-gradient-approximation and a double-zeta-polarized basis set are used [33]. A mesh cutoff parameter of 220 Ry has been used for the calculations along with a very large box to avoid interaction of the images. The geometry optimization was
Carbene-functionalized diamondoids
We begin with the analysis of the structural modifications of carbene-functionalized diamondoids as the one shown in Fig. 1. We monitor the bond-length of the carbon and nitrogen atoms in the carbene unit (imidazolylidene-C3N2H6) which is similar in all the three cases (close to 1.46 Å) except (121)-tetramantane ((121)C22H28), in which the bond shrinks to 1.36 Å. A similar behavior is observed in the bond-angle between NCN of the carbene ring, which shows a variation of 2∘ in case of
Summary
In this work, within the framework of density functional theory we have modeled and investigated the functionalization possibilities of diamondoids (CxHy+1) with a carbene unit C3N2H6, the imidazolylidene molecule. Diamondoids from adamantane up to (121)-tetramantane were modeled. Specifically, two types of molecules are studied, the carbene-functionalized diamondoids (C3N2H6CxHy) and complexes of these with a metal atom M (C3N2H4CxHyM). For the latter, noble metals (Au, Ag, Cu, and Pt) were
Acknowledgments
A. N. is thankful to G. Sivaraman for critically discussing the results. The authors acknowledge support from the German Funding Agency (Deutsche Forschungsgemeinschaft-DFG) as a part of the collaborative network SFB 716 “Dynamic simulations of systems with large particle numbers”. This work was performed on the computational resource ForHLR Phase I funded by the Ministry of Science, Research and the Arts Baden-Württemberg and DFG.
References (36)
- et al.
Systematic classification and nomenclature of diamond hydrocarbons-I
Tetrahedron
(1978) - et al.
Negative-electron-affinity diamondoid monolayers as high-brilliance source for ultrashort electron pulses
Chem. Phys. Lett.
(2010) - et al.
Stability: a key issue for self-assembled monolayers on gold as thin-film coatings and nanoparticle protectants
Colloids Surf. A Physicochem. Eng. Aspects
(2011) - et al.
Carbenes: synthesis, properties, and organometallic chemistry
Coord. Chem. Rev.
(2009) - et al.
Nickel N-heterocyclic carbene complexes and their utility in homogeneous catalysis
Inorganica Chim. Acta
(2015) - et al.
Iridium, ruthenium, and palladium complexes containing a mesoionic fused imidazolylidene ligand
J. Organomet. Chem.
(2015) - et al.
Isolation and Structure of Higher Diamondoids, Nanometer-Sized Diamond Molecules
Science
(2003) - et al.
Diamonds are a Chemist's Best Friend: Diamondoid Chemistry Beyond Adamantane
Angew. Chem. Int. Ed.
(2008) - et al.
The mechanism of diamond nucleation from energetic species
Science
(2002) Monochromatic electron photoemission from diamondoid monolayers
Science
(2007)
Spatially resolved electronic and vibronic properties of single diamondoid molecules
Nat. Mater
Diamondoid molecules: with applications in biomedicine, materials science, nanotechnology and petroleum science
Phys. Today
Diamond fragments as building blocks of functional nanostructures
Phys. Rev. B
Experimental and theoretical study of the absorption properties of thiolated diamondoids
J. Chem. Phys.
The influence of a single thiol group on the electronic and optical properties of the smallest diamondoid adamantane
J. Chem. Phys.
Electron Emission from Diamondoids: A Diffusion Quantum Monte Carlo Study
Phys. Rev. Lett.
Nanoparticles: Scaffolds for Molecular Recognition
Chem.–A Eur. J.
New Approaches to Nanofabrication: Molding, Printing, and Other Techniques
Chem. Rev.
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