Various metallabenzene complexes, analogues of benzene where one CH unit has been replaced by an organometallic fragment, have been reported in the literature. A detailed theoretical investigation on the chemistry of these complexes is presented here. This includes an evaluation of their aromaticity, the mechanisms of formation of osmium, iridium, and platinum metallabenzene complexes, and one intriguing aspect of their chemistry, the formation of cyclopentadienyl (Cp) complexes. X-ray photoelectron spectroscopy (XPS) measurements on two osmabenzene examples are also presented. In addition, diffuse functions for use with the SDD and SDB-cc-pVDZ basis set-RECP combinations are presented for the transition metals.
The potential triple-halogen-bond acceptor, sym-triiodo-trifluorobenzene IFB (1), has been co-crystallized with a
series of bipyridyl derivatives (2−4) to gain insight to the factors controlling formation of multiple halogen bonds with a single
aromatic system. Co-crystals 5−7 were obtained that consistently contained two N···I halogen bonds. The reluctance to the formation
of a supramolecular assembly having a third N···I halogen bond does not depend on the size of the bispyridine donor systems
(2−4). Apparently, there are limitations to the number of halogen bonds that can be formed with a single aromatic halogen donor.
The solid-state structure of co-crystal (5) contains short I···F contacts of 2.96 and 3.05 Å. DFT calculations were performed at the
PBE0/(apc1-aSDBDZ)//PBE0/(pc1-SDBDZ) level of theory to investigate the nature of the interaction between the pyridine nitrogen
and IFB (1). These calculations reveal a weakening of N···I interactions as more pyridine moieties coordinate to the IFB (1), which
might be a contributing factor to the consistent formation of two rather than three N···I halogen bonds.
A new series of stilbene-based chromophores have been used to prepare structurally related siloxane-based monolayers in order to determine which factors control the intermolecular chromophore-chromophore interactions in the solid state. The reaction of chromophore precursors 4-styrylpyridine (1), 4-[2-(4bromophenyl)-vinyl]-pyridine (2), 4-(2-naphthalen-1-ylvinyl)-pyridine (3), 4-(2-anthracen-9-ylvinyl)-pyridine (4), and 4-(2-pyren-2-ylvinyl)-pyridine ( 5) with excess 3-iodo-n-propyl-1-trimethoxysilane resulted in the corresponding salts 6-10 in quantitative yield. The assembly of chromophores 6-10 on hydrophilic substrates from solution resulted in the formation of densely packed monolayers with a film thickness of ∼1 nm. The average chromophore density (∼1 chromophore/50 Å 2 ) is well within the range that allows π-π stacking to occur. Transmission UV-vis spectroscopy of the siloxane-based films shows that the intermolecular interactions are a function of the aryl groups (e.g., phenyl, bromophenyl, naphthalene, anthracene, and pyrene). Relatively weak electronic interactions occur between the surface-bound chromophores 6, 7, and 10, whereas strong electronic interactions occur between surface-bound chromophores 8 and 9. The series of monolayers on sodium lime glass and polished silicon is characterized by a combination of physicochemical methods including X-ray photoelectron spectroscopy, advancing aqueous contact angle measurements, optical spectroscopy, atomic force microscopy, and synchrotron X-ray reflectivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.