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You searched for subject:(Stable carbenes). Showing records 1 – 2 of 2 total matches.

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University of Texas – Austin

1. -5909-4924. Modification of N-heterocyclic carbene scaffolds : insights into reactivity and electronic properties.

Degree: PhD, Chemistry, 2017, University of Texas – Austin

Starting from the initial efforts to prepare, study, and utilize carbenes, the choice of substituents has been recognized as a critical factor in determining their properties. Following the isolation of stable carbenes, a further aspect of design has become apparent; creation of a supporting scaffold to provide influence over the carbene’s reactivity and electronic properties as well as providing a protective envelope to ensure stability. Modification of previous N-heterocyclic carbene scaffolds to provide a new range of diamidocarbenes, which demonstrated enhance electrophilic properties. Further elaboration of these scaffolds has allowed the synthesis of novel carbenes with tailored properties. A series of six-membered carbenes featuring adjoining amino and/or amido groups were studied to determine the effect of substituent modification. A mono-amino/amido carbene (MAAC), a diamidocarbenes, and a diaminocarbene were systematically compared using crystallographic, spectroscopic, electrochemical, and density functional theory methods. Using single crystal X-ray diffraction analysis, the free MAAC was found to exhibit inequivalent nitrogen-carbon bond lengths Iridium complexes of the carbenes were also evaluated and the collected data revealed that the introduction of carbonyl groups to the carbene-containing scaffold had a nearly linear, additive effect on the E [subscript 1/2] potential of the carbene-ligated iridium I/II redox couple (+165 mV per carbonyl added) as well as the TEP value of the corresponding carbene-Ir(CO)₂Cl complex. Beyond attenuated ligand donicity, the introduction of carbonyl groups expanded the carbene’s reactivity: unlike prototypical NHCs, the MAAC was found to couple to isonitriles to form the respective ketenimines. Additionally, remotely substituted diamidocarbenes (DACs) were prepared and characterized. These carbenes were compared to their parent carbene via spectroscopic and density functional theory methods, and subjected to reactivity trials to determine the effects of remote substitution. Spectroscopic examination of the carbene-Ir(CO)₂Cl complexes demonstrated a difference in TEP value, indicating a small effect of substitution on the carbene’s electronic state. However, treatment of the differently substituted carbenes with substrates known to react with the parent DAC indicated no significant difference in reactivity scope; additionally, computational methodology demonstrated similarities in calculated geometries and orbital energy levels. Advisors/Committee Members: Willson, C. G. (C. Grant), 1939- (advisor), Bielawski, Christopher W (committee member), Anslyn, Eric V (committee member), Evans, Neal J (committee member), Humphrey, Simon M (committee member), Martin, Stephen F (committee member).

Subjects/Keywords: Carbenes; Stable carbenes; Electrophilic carbenes

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

-5909-4924. (2017). Modification of N-heterocyclic carbene scaffolds : insights into reactivity and electronic properties. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/72807

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16th Edition):

-5909-4924. “Modification of N-heterocyclic carbene scaffolds : insights into reactivity and electronic properties.” 2017. Doctoral Dissertation, University of Texas – Austin. Accessed December 16, 2019. http://hdl.handle.net/2152/72807.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7th Edition):

-5909-4924. “Modification of N-heterocyclic carbene scaffolds : insights into reactivity and electronic properties.” 2017. Web. 16 Dec 2019.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-5909-4924. Modification of N-heterocyclic carbene scaffolds : insights into reactivity and electronic properties. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2017. [cited 2019 Dec 16]. Available from: http://hdl.handle.net/2152/72807.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-5909-4924. Modification of N-heterocyclic carbene scaffolds : insights into reactivity and electronic properties. [Doctoral Dissertation]. University of Texas – Austin; 2017. Available from: http://hdl.handle.net/2152/72807

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete


Queens University

2. Narouz, Mina. N-Heterocyclic carbenes as novel ligands for metal surfaces, nanoparticles and nanoclusters .

Degree: Chemistry, Queens University

N-heterocyclic carbenes (NHCs) are carbon-based organic molecules that have been extensively employed as ligands for transition metal complexes for the past twenty years. They form stable metal complexes that can be used under conditions where other complexes would decompose. Despite their widespread use in transition metal chemistry, until recently, the employment of NHCs on metal surfaces has remained largely unexplored. This thesis describes the use of NHCs as novel ligands to functionalize planar metallic surfaces, curved gold nanoparticles and nanoclusters. We developed novel methods for the synthesis of air-stable benzimidazolium bicarbonates as single-source NHC precursors that were used to form high-quality films on gold surfaces. This enabled the facile preparation of identical monolayers to those formed using free NHCs but in the air, using undried solvents, with a single component precursor. Subsequently, we employed this simple generation of NHC monolayers to prepare various gold biosensors and functionalize other metals such as copper, platinum, and magnesium enabling unprecedented insight into structure-property relationships. In addition, we described the synthesis of amphiphilic NHC-functionalized gold nanoparticles where their self-assembly in polar solvents allowed the tuning of the collective optical properties and boosted the overall stability. Furthermore, we reported the first examples of gold superatoms, known as nanoclusters, protected by NHCs either by a displacement reaction or by the direct reduction NHC-gold complexes. The resulting NHC-phosphine-protected Au11 clusters were significantly stable and electrocatalytically activate toward the reduction of CO2 whereas the all NHC-stabilized Au13 clusters had exceptionally high photoluminescence greater than the most luminescent ligand-protected gold nanoclusters. We also obtained the first crystal structures of this new class of materials and showed the effect of the NHCs design on the cluster properties. The reported NHC-stabilized metallic materials in this thesis have unique properties that can open the door for further potential applications in biosensing, bio-imaging, microelectronics and catalysis.

Subjects/Keywords: N-Heterocyclic carbenes; surfaces; nanoparticles; nanoclusters; materials chemistry; metal; stable materials; self-assembled monolayers; clusters; gold; copper; magensium; platinum; sensors; fluorescence; surface chemistry; self-assembly; catalysis

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Narouz, M. (n.d.). N-Heterocyclic carbenes as novel ligands for metal surfaces, nanoparticles and nanoclusters . (Thesis). Queens University. Retrieved from http://hdl.handle.net/1974/26489

Note: this citation may be lacking information needed for this citation format:
No year of publication.
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Narouz, Mina. “N-Heterocyclic carbenes as novel ligands for metal surfaces, nanoparticles and nanoclusters .” Thesis, Queens University. Accessed December 16, 2019. http://hdl.handle.net/1974/26489.

Note: this citation may be lacking information needed for this citation format:
No year of publication.
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Narouz, Mina. “N-Heterocyclic carbenes as novel ligands for metal surfaces, nanoparticles and nanoclusters .” Web. 16 Dec 2019.

Note: this citation may be lacking information needed for this citation format:
No year of publication.

Vancouver:

Narouz M. N-Heterocyclic carbenes as novel ligands for metal surfaces, nanoparticles and nanoclusters . [Internet] [Thesis]. Queens University; [cited 2019 Dec 16]. Available from: http://hdl.handle.net/1974/26489.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
No year of publication.

Council of Science Editors:

Narouz M. N-Heterocyclic carbenes as novel ligands for metal surfaces, nanoparticles and nanoclusters . [Thesis]. Queens University; Available from: http://hdl.handle.net/1974/26489

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
No year of publication.

.