Ring Carbon Atoms Research Articles

"Through-Space" Relativistic Effects on NMR Chemical Shifts of Pyridinium Halide Ionic Liquids.

We have investigated, using two-component relativistic density functional theory (DFT) at ZORA-SO-BP86 and ZORA-SO-PBE0 level, the occurrence of relativistic effects on the 1 H, 13 C, and 15 N NMR chemical shifts of 1-methylpyridinium halides [MP][X] and 1-butyl-3-methylpyridinium trihalides [BMP][X3 ] ionic liquids (ILs) (X=Cl, Br, I) as a result of a non-covalent interaction with the heavy anions. Our results indicate a sizeable deshielding effect in ion pairs when the anion is I- and I3- . A smaller, though nonzero, effect is observed also with bromine while chlorine based anions do not produce an appreciable relativistic shift. The chemical shift of the carbon atoms of the aromatic ring shows an inverse halogen dependence that has been rationalized based on the little C-2s orbital contribution to the σ-type interaction between the cation and anion. This is the first detailed account and systematic theoretical investigation of a relativistic heavy atom effect on the NMR chemical shifts of light atoms in the absence of covalent bonds. Our work paves the way and suggests the direction for an experimental investigation of such elusive signatures of ion pairing in ILs.

High Sodium-Storage Capacity in MOF Achieved by Activating Aromatic Rings

In a recent issue of Chem, Yunhui Huang and Chun Fang from Huazhong University of Science and Technology, Jianjun Liu from Shanghai institute of Ceramics, Chinese Academy of Sciences, China, and their co-authors have designed a stable 3D wavy-layered metal organic framework with a high sodium-insertion capacity of 357 mAh g−1 as an electrode material. As evidenced by experimental work and density functional theory (DFT) calculations, a stepwise sodium storage mechanism is proposed, i.e., Na+ ions are first chemisorbed by the C = O groups on aromatic rings, and then interact with the sp2-hybridized carbon atoms of the aromatic rings. With a coordination with metal ions, the aromatic rings are successfully activated as redox sites for reversible Na+ insertion.

Theoretical Study on the Hydrogenation Mechanisms of Model Compounds of Heavy Oil in a Plasma-Driven Catalytic System

Heavy oil will likely dominate the future energy market. Nevertheless, processing heavy oils using conventional technologies has to face the problems of high hydrogen partial pressure and catalyst deactivation. Our previous work reported a novel method to upgrade heavy oil using hydrogen non-thermal plasma under atmospheric pressure without a catalyst. However, the plasma-driven catalytic hydrogenation mechanism is still ambiguous. In this work, we investigated the intrinsic mechanism of hydrogenating heavy oil in a plasma-driven catalytic system based on density functional theory (DFT) calculations. Two model compounds, toluene and 4-ethyltoluene have been chosen to represent heavy oil, respectively; a hydrogen atom and ethyl radical have been chosen to represent the high reactivity species generated by plasma, respectively. DFT study results indicate that toluene is easily hydrogenated by hydrogen atoms, but hard to hydrocrack into benzene and methane; small radicals, like ethyl radicals, are prone to attach to the carbon atoms in aromatic rings, which is interpreted as the reason for the increased substitution index of trap oil. The present work investigated the hydrogenation mechanism of heavy oil in a plasma-driven catalytic system, both thermodynamically and kinetically.

Selectively nitrogen-doped carbon materials as superior metal-free catalysts for oxygen reduction

Doping with pyridinic nitrogen atoms is known as an effective strategy to improve the activity of carbon-based catalysts for the oxygen reduction reaction. However, pyridinic nitrogen atoms prefer to occupy at the edge or defect sites of carbon materials. Here, a carbon framework named as hydrogen-substituted graphdiyne provides a suitable carbon matrix for pyridinic nitrogen doping. In hydrogen-substituted graphdiyne, three of the carbon atoms in a benzene ring are bonded to hydrogen and serve as active sites, like the edge or defect positions of conventional carbon materials, on which pyridinic nitrogen can be selectively doped. The as-synthesized pyridinic nitrogen-doped hydrogen-substituted graphdiyne shows much better electrocatalytic performance for the oxygen reduction reaction than that of the commercial platinum-based catalyst in alkaline media and comparable activity in acidic media. Density functional theory calculations demonstrate that the pyridinic nitrogen-doped hydrogen-substituted graphdiyne is more effective than pyridinic nitrogen-doped graphene for oxygen reduction.

CH activations in aldehydes in reactions with Ru5(μ5-C)(CO)15

The reaction of Ru5(μ5-C)(CO)15, 1 with benzaldehyde yielded two new pentaruthenium carbido cluster compounds: Ru5(μ5-C)(CO)14[η2-O=C(H)C6H4](μ-H), 2 and Ru5(μ5-C)(CO)14(μ-η2-O=CPh)(μ-H), 3 containing open Ru5C cluster complexes formed by the activation of two different C-H bonds of the benzaldehyde molecule. Compound 2 contains a chelating, ortho-metallated benzaldehyde ligand coordinated to an open Ru5C cluster that is coordinated by the aldehyde oxygen atom and one of the ortho-positioned carbon atoms of the phenyl ring that was formed by loss of a CO ligand and an oxidative addition of the ortho-C-H bond of the phenyl ring to the metal atom. Compound 3 is an isomer of 2 that contains an O=C-coordinated, η2-bridging benzoyl ligand across the open edge of the Ru5C cluster formed by C-H activation at the aldehyde formyl group. The reaction of 1 with trans-cinnamaldehyde yielded two complexes: Ru5(μ5-C)(CO)14[η2-O=C(H)CH=CPh](μ-H), 4 and Ru5(μ5-C)(CO)14[μ-η2-O=CC(H) = C(H)Ph](μ-H), 5. Compound 4 contains an open Ru5 cluster with a chelating cinnamoyl ligand formed by coordination of the aldehyde oxygen atom and the β–carbon atom of the alkene double bond formed by a C-H activation at the alkene atom. Compound 5 contains a η2-bridging, O=C coordinated cinnamoyl group formed by C-H activation at the aldehyde formyl group. The reactions of 1 with furfural and 5-hydroxymethylfurfural yielded similar complexes: Ru5(μ5-C)(CO)14(μ-η2-O=CC4OH3)(μ-H), 6 and Ru5(μ5-C)(CO)14[μ-η2-O=CC4OH2(CH2OH)](μ-H), 7, respectively with each one containing bridging, O=C coordinated acyl ligand formed by C-H activation at the aldehyde formyl group. All of the new compounds were characterized by single-crystal X-ray diffraction analyses.

Reaction Mechanisms of 2-Butanol Dehydration over a Phosphorus-Containing Activated Carbon Acid Catalyst

The reaction mechanisms for the carbon-based acid catalytic conversion of 2-butanol into dehydration and dehydrogenation products (alkene derivatives and ketone) have been theoretically studied by assuming that the acid site is a dihydrogen phosphate group bonded to one of the carbon atoms of the central ring of anthracene. The structural model of the active site of the surface of the catalyst reproduces properly the experimental results. Kinetic and thermodynamic magnitudes have been obtained by using standard expressions of Eyring’s transition-state theory and statistical thermodynamics. Interpretation of the calculations (molecular charges, geometries, and energies) demonstrates that the dehydration reaction process is an E2 mechanism (one-step reaction) with strong character of E1 mechanism (two-step reaction). The study of the mechanism has been carried out by applying density functional theory with the metaexchange–correlation functional M06-2X. The reactants and products connected by the respective...

Theoretical study of the mechanism and regioselectivity of the alkylation reaction of the phenoxide ion in polar protic and aprotic solvents

Abstract Alkylation of the phenoxide ion in the solution phase can take place on the oxygen atom (O-alkylation) and the carbon atoms of the aromatic ring in the ortho- and para-positions (C-alkylation). The reaction outcome depends on the alkylating molecule and the solvent. This work presents a density functional theory calculation (X3LYP and M08-SO functionals) of the possible reaction pathways for alkylation of phenoxide ions with ethyl chloride in the following solvents: water, methanol, and dimethyl sulfoxide. The solvent effect was included through the SMD and PCM models. Our results pointed out that O-alkylation was much more favorable than C-alkylation in the gas phase. Solvent effect favors C-alkylation, although it was unable to change the reactivity preference of O-alkylation, even in aqueous solution. Alkylation on the meta-carbon atom corresponded to a second-order saddle point and was the most unfavorable pathway. The calculations indicated that only O-alkylation would be observed, with an activation free energy of 23.6 kcal mol−1 in dimethyl sulfoxide solution, in good agreement with the experimental barrier of 20.8 kcal mol−1.

Sterically Demanding Phosphines with 2,6-Dibenzhydryl-4-methylphenyl Core: Synthesis of RuII, PdII, and PtII Complexes, and Structural and Catalytic Studies.

The synthesis of sterically demanding aminophosphine and phosphinite ligands Ar*NHPPh2 (1) and Ar*OPPh2 (2), based on 2,6-dibenzhydryl-4-methylphenyl core having bulky benzhydryl groups, and their RuII, PdII and PtII complexes is described. The reactions of 1 and 2 with [Ru(η6- p-cymene)Cl2]2 in 2:1 molar ratios produced mononuclear complexes [RuCl2{(η6- p-cymene)PPh2-EAr*}-κ1-P] (E = NH (3) and O (4)). Interestingly, complexes 3 and 4, upon refluxing in chlorobenzene, displace the p-cymene ring by one of the phenyl rings of side arms, forming rare η6-arene coordinated tethered complexes [RuCl2{(PPh2-EAr*)-κ1-P-η6-arene}] (E = NH (5) and O (6)). Treatment of 1 and 2 with [M(COD)Cl2] [M = Pd, Pt] in 2:1 ratios afforded mononuclear complexes [MCl2{(PPh2EAr*)-κ1-P}2] (E = NH, M= Pd (7), Pt (8); E = O, M= Pd (9), Pt (10)). Similarly, 1:1 reactions of 1 and 2 with [Pd(COD)Cl2] produced chloro-bridged dinuclear complexes [PdCl2{(PPh2EAr*)-κ1-P}]2 (E = NH (11) and O (12)), whereas [Pt(COD)Cl2] yielded only the mononuclear complexes 8 and 10. The reactions of 1 and 2 with [Pd(η3-C3H5)Cl]2 in 2:1 molar ratios produced the mononuclear complexes [PdCl{(η3-C3H5)(PPh2EAr*)-κ1-P}] (E = NH (13) and O (14)). Many of these complexes have been structurally characterized, which show C-H···π interactions between the methine hydrogen of the benzhydryl and with one of the carbon atoms of the phenyl ring attached to the phosphorus center. The complex [RuCl2{(η6- p-cymene)PPh2-NHAr*}-κ1-P] (3) shows very short C-H···π interactions of 2.36 Å; in addition, C-H···M interactions were observed between the methine hydrogen of one of the benzhydryl groups and palladium centers in 11 and 13. The tethered ruthenium complex 5 is found to be an excellent catalyst for the catalytic oxidation of various styrene derivatives.

Halogen Bonds of 4-Iodosydnones in Solution Deduced from 13C-NMR Spectra

The ability of 4-iodosydnones to form halogen bonds with Lewis bases in solution was deduced from significant changes in the 13C-NMR chemical shift of the carbon atom of the sydnone ring which is bonded to iodine.

Synthesis and amelioration of inflammatory paw edema by novel benzophenone appended oxadiazole derivatives by exhibiting cyclooxygenase-2 antagonist activity

Ten new 2(4-hydroxy-3-benzoyl) benzamide-5-phenyl-1,3,4-oxadiazole derivatives (10a–j) were synthesized by coupling 3-benzoyl-4-hydroxybenzoic acid (5) with 2-amino-5-phenyl-1,3,4-oxadiazoles (9a–j). The structures of these compounds were confirmed by IR, 1H, 13C NMR, and mass spectra, and also by elemental analyses. The anti-inflammatory activity of the compounds 10a–j were investigated by screening them against human red blood cells (HRBC) in-vitro. The results reveal that among this series, compound 10j with hydroxy substituent, particularly at the ortho position of the phenyl ring attached to the 5th carbon atom of the oxadiazole ring possess significant membrane stabilizing activity in comparison with the control. Further, in-vivo chick chorioallantoic membrane (CAM) and rat corneal anti-angiogenesis assays were performed to assess the effect of compound 10j on endothelial cell migration. This confirmed that compound 10j inhibits the proliferation of endothelial cells. Anti-inflammatory studies detected the amelioration of carrageen induced rat hind paw edema. Further in-vivo and in-silico approaches revealed the inhibition of inflammatory marker enzyme cyclooxygenase-2 (Cox-2) and myleoperoxidase (MPO). The study reports that the compound 10j effectively act against the inflammatory mediated anti-angiogenic disorders which could be translated into a new drug in future.

Indium-Catalyzed Annulation of o-Acylanilines with Alkoxyheteroarenes: Synthesis of Heteroaryl[b]quinolines and Subsequent Transformation to Cryptolepine Derivatives.

We disclose herein the first synthetic method that is capable of offering heteroaryl[b]quinolines (HA[b]Qs) with structural diversity, which include tricyclic and tetracyclic structures with (benzo)thienyl, (benzo)furanyl, and indolyl rings. The target HA[b]Q is addressed by the annulation of o-acylanilines and MeO–heteroarenes with the aid of an indium Lewis acid that effectively works to make two different types of the N–C and C–C bonds in one batch. A series of indolo[3,2-b]quinolines prepared here can be subsequently transformed to structurally unprecedented cryptolepine derivatives. Mechanistic studies showed that the N–C bond formation is followed by the C–C bond formation. The indium-catalyzed annulation reaction thus starts with the nucleophilic attack of the NH2 group of o-acylanilines to the MeO-connected carbon atom of the heteroaryl ring in an SNAr fashion, and thereby the N–C bond is formed. The resulting intermediate then cyclizes to make the C–C bond through the nucleophilic attack of the heteroaryl-ring-based carbon atom to the carbonyl carbon atom, providing the HA[b]Q after aromatizing dehydration.

Crystal structure of 9,9′-(4,4′-(silinane-1,1-diyl)bis(4,1-phenylene))bis(9H-carbazole) and its photophysical and electrochemical properties

The title compound 9,9′-(4,4′-(silinane-1,1-diyl)bis(4,1-phenylene))bis(9H-carbazole) (6-bisCz) has been designed and prepared to investigate its crystal structure and photophysical and electrochemical properties. 6-bisCz is crystallized in the centrosymmetric space group P−1. Interestingly, the asymmetric unit contains two molecules (Z′ = 2), and hence, the entire cell contains four units (Z = 4). The central silicon atom was arranged in pseudo-tetrahedral geometry defined by the two ipso-carbon atoms of the phenyl groups and two carbon atoms in the endocyclic hexyl ring, with average bond angles of 104.5(1)° and 108.5(1)°, respectively. UV/Vis absorption and photoluminescence spectra showed that the central silicon atom successfully disconnected electronic communication between the two peripheral phenylcarbazole units, yielding similar absorption and emission spectra to an unsubstituted carbazole monomer. The influence of the central silicon atom between the two phenylcarbazole units is also simulated by density functional theory calculations. Finally, electrochemical properties of 6-bisCz were investigated, and the analysis shows that an electropolymerized film was successfully formed during the electrochemical process.

Structural, electronic structure and antibacterial properties of graphene-oxide nano-sheets

Correlation between the structural/electronic structure properties and bio-activity of graphene-based materials need to be thoroughly evaluated before their commercial implementation in the health and environment precincts. To better investigate the local hybridization of sp2/sp3 orbitals of the functional groups of graphene-oxide (GO) and their execution in the antimicrobial mechanism, we exemplify the antibacterial activity of GO sheets towards the Escherichia coli bacteria (E. coli) by applying the field-emission scanning electron microscopy (FESEM), near edge X-ray absorption fine structure (NEXAFS) and scanning transmission X-ray microscope (STXM) techniques. C K-edge and O K-edge NEXAFS spectra have revealed lesser sp2 carbon atoms in the aromatic ring and attachment of functional oxygen groups at GO sheets. Entrapment of E. coli bacteria by GO sheets is evidenced by FESEM investigations and has also been corroborated by nano-scale imaging of bacteria using the STXM. Spectroscopy evidence of functional oxygen moieties with GO sheets and physiochemical entrapment of E. coli bacteria have assisted us to elaborate the mechanism of cellular oxidative stress-induced disruption of bacterial membrane.

Effect of Binding on Enantioselectivity of Epoxide Hydrolase.

Molecular dynamics simulations and free energy calculations have been used to investigate the effect of ligand binding on the enantioselectivity of an epoxide hydrolase (EH) from Aspergillus niger. Despite sharing a common mechanism, a wide range of alternative mechanisms have been proposed to explain the origin of enantiomeric selectivity in EHs. By comparing the interactions of ( R)- and ( S)-glycidyl phenyl ether (GPE) with both the wild type (WT, E = 3) and a mutant showing enhanced enantioselectivity to GPE (LW202, E = 193), we have examined whether enantioselectivity is due to differences in the binding pose, the affinity for the ( R)- or ( S)- enantiomers, or a kinetic effect. The two enantiomers were easily accommodated within the binding pockets of the WT enzyme and LW202. Free energy calculations suggested that neither enzyme had a preference for a given enantiomer. The two substrates sampled a wide variety of conformations in the simulations with the sterically hindered and unhindered carbon atoms of the GPE epoxide ring both coming in close proximity to the nucleophilic aspartic acid residue. This suggests that alternative pathways could lead to the formation of a ( S)- and ( R)-diol product. Together, the calculations suggest that the enantioselectivity is due to kinetic rather than thermodynamic effects and that the assumption that one substrate results in one product when interpreting the available experimental data and deriving E-values may be inappropriate in the case of EHs.

Tunability of Open-Shell Character, Charge Asymmetry, and Third-Order Nonlinear Optical Properties of Covalently Linked (Hetero)Phenalenyl Dimers.

Tunability of the open-shell character, charge asymmetry, and third-order nonlinear optical (NLO) properties of covalently linked (hetero)phenalenyl dimers are investigated by using the density functional theory method. By changing the molecular species X and substitution position (i, j) for the linker part, a variety of intermonomer distances R and relative alignments between the phenalenyl dimers can be realized from the geometry optimizations, resulting in a wide-range tuning of diradical character y and charge asymmetry. It is found that the static second hyperpolarizabilities along the stacking direction, γyyyy , are one-order enhanced for phenalenyl dimer systems exhibiting intermediate y, a feature that is in good agreement with the "y-γ correlation". By replacing the central carbon atoms of the phenalenyl rings with a boron or a nitrogen, we have also designed covalently linked heterophenalenyl dimers. The introduction of such a charge asymmetry to the open-shell systems, which leads to closed-shell ionic ground states, is found to further enhance the γyyyy values of the systems having longer intermonomer distance R with intermediate ionic character, that is, charge asymmetry. The present results demonstrate a promising potential of covalently linked NLO dimers with intermediate open-shell/ionic characters as a new building block of highly efficient NLO systems.

Scalable synthesis and properties of 7-methyl- 4-azaindole

Abstract An approach to the synthesis of 7-methyl-4-azaindole, which is a valuable building block for drug discovery programs, is described. The method relies on using a bromine atom as a ‘place holding group’ for one of the carbon atoms of the pyridine ring throughout the reaction sequence, and it is removed only upon the final reductive cyclization leading to the azaindole ring. Exhaustive hydrogenation of the target product proceeds in a diastereoselective manner and leads to a bicyclic conformationally restricted diamine derivative.

Search Of High Active And Low Toxic Newly Synthesized Derivatives Of Piperidine For Regional Anesthesia

comparative assessment of local anesthetic activity of newly synthesized derivatives of piperidine for regional anesthesia, depending on their chemical structure. local anesthesia was determined by the method of “tail-flick” on white rats. For research of activity of the compound at the particular type of anesthesia the great important index is duration of complete anesthesia. The duration of complete anaesthesia of LAS-174 was similar to trimecaine, slightly higher than that of novocaine and a little bit less than lidocaine (p>0.05). Total duration of action of LAS-174 is higher than the novocaine and trimekain, and a few exceeding that of lidocaine (p>0.05). LAS-175 index of full anesthesia was 2 times higher than trimekain, 2.5 times than novocaine and a few more than lidocaine (p>0.05). By the total duration this compound exceeds the matched values of trimethoprim, lidocaine and novocaine in 3.4, 1.9 and 4.6 times, respectively. Replacement of the propyl radical to Amillic in the side chain at the 4-th carbon atom of the piperidine ring enhances local activity by the similar toxicity. In 1% solution duration of anesthesia of LAS-190 is similar to the trimecaine and slightly lower than the lidocaine. LAS-189 shows a weaker effect than trimekain and lidocaine (p>0.05). LAS-189 and 190 by the duration of anesthesia was more effective than novocaine, but this difference is not statistically significant. Replacement of the propyl radical (LAS-189) to the phenyl (LAS-190) contributes to increase of local anesthetic activity, especially for the total duration. Acute toxicity of LAS-189 is 750±of 35.56, LAS-190 - 1284±43,87. the Introduction of a cyclopropane radical at the triple bind of the piperidine ring leads to increased local anesthetic effect, weighting of the radical at the 4th carbon atom contributes to the growth of activity and lower toxicity.

Simulations on the structure, vibrations and electronic properties of 1,2–epoxy–3–phenoxy propane and 1,2–epoxy–3–( p –tolyloxy)propane by FT–IR, FT–Raman, FT–NMR and DFT methods

Abstract Complete structural, electronic and vibrational properties of 1,2–epoxy–3–phenoxy propane (EPOP) and 1,2–epoxy–3–(p–tolyloxy)propane (ETOP) molecules have been investigated with the help of FT–IR, FT–Raman and FT–NMR spectra of the compounds with the support of the theoretical calculations carried out by DFT/B3LYP method of calculations with 6–311 + + G** and cc–pVTZ basis sets. Various possible conformers of the compounds are determined by analyzing the potential energy profile. In EPOP, the stable conformer I is more stable than the second II by 0.1776 kcal mol–1. Similarly, the conformer I of ETOP is more stable than the conformer II 0.8435 kcal mol–1. The various modes of vibrational frequencies are assigned and analysed with the help of FT–IR and FT–Raman spectra. The electronic properties, such as HOMO and LUMO energies are determined. In both the cases of EPOP and ETOP, the HOMO space distribution reveals that all the carbon atoms of the phenyl ring, the methyl carbon atom and the methylene hydrogen atoms H8 and H9 are more favourable for electrophilic attack. The lone pair donor orbital, n(O10) → π*C11–C16 interaction in EPOP is strongly stabilised by 29.34 kcal mol–1. In the case of ETOP compound, πC12–C13 → π*C11–C16 interaction has more stabilisation energy, 21.34 kcal mol–1. The stabilisation energy of lone pair donor orbital, n(O10) → σ*C11–C16 is 28.80 kcal mol–1. 1H and 13C chemical shifts of the molecules are calculated by GIAO method and discussed. For EPOP, the hydrogen atoms H4, H5 and H6 present in the epoxy ring shows peaks at 2.72, 2.85 and 3.32 ppm, respectively. In the case of ETOP the epoxy hydrogen shows up field peak at 2.70, 2.84 and 2.30 ppm, because of the presence of hyperconjugative effect of the methyl group. The chemical reactivity and site selectivity of the molecule has been determined with the help of global and local reactivity descriptors. The Δfk, Δsk and Δωk values of ETOP suggests that C14 and C11 carbon atoms are more prone to nucleophilic attack while in EPOP the Δfk and Δωk values shows that C14 and C11 is the active sites for the nucleophilic attack but Δsk is only favourable for C11 and not for C14 atom.

Revealing the Initial Chemistry of Soot Nanoparticle Formation by ReaxFF Molecular Dynamics Simulations

This work presents long time ReaxFF MD simulations of fuel-rich combustion for up to 10 ns to explore the initial mechanism of soot nanoparticle formation. A 24-component rocket propellant 1 (RP-1) model based on the major components of RP-1 fuel was employed. Simulations were performed by GPU-accelerated code GMD-Reax, and reactions therein were revealed with the aid of VARxMD. Simulated evolution of physical and chemical properties of the largest molecule exhibits the overall structural transitions of three stages for incipient ring formation, nucleation, and graphitization from fuel molecules to the formation of a single soot nanoparticle. The incipient ring formation takes place in stage 1 by large ring generation from activated aliphatic polyyne-like chains, ring number increase from internal bridging between carbon atoms of large rings, and consequent formation of PAH-like molecules with aliphatic side chains. Nucleation of a nanoparticle in stage 2 is the result of coalescence of PAH-like molecules...

Retained Carrier-Mobility and Enhanced Plasmonic-Photovoltaics of Graphene via ring-centered η6 Functionalization and Nanointerfacing.

Binding graphene with auxiliary nanoparticles for plasmonics, photovoltaics, and/or optoelectronics, while retaining the trigonal-planar bonding of sp2 hybridized carbons to maintain its carrier-mobility, has remained a challenge. The conventional nanoparticle-incorporation route for graphene is to create nucleation/attachment sites via "carbon-centered" covalent functionalization, which changes the local hybridization of carbon atoms from trigonal-planar sp2 to tetrahedral sp3. This disrupts the lattice planarity of graphene, thus dramatically deteriorating its mobility and innate superior properties. Here, we show large-area, vapor-phase, "ring-centered" hexahapto (η6) functionalization of graphene to create nucleation-sites for silver nanoparticles (AgNPs) without disrupting its sp2 character. This is achieved by the grafting of chromium tricarbonyl [Cr(CO)3] with all six carbon atoms (sigma-bonding) in the benzenoid ring on graphene to form an (η6-graphene)Cr(CO)3 complex. This nondestructive functionalization preserves the lattice continuum with a retention in charge carrier mobility (9% increase at 10 K); with AgNPs attached on graphene/n-Si solar cells, we report an ∼11-fold plasmonic-enhancement in the power conversion efficiency (1.24%).