scholarly journals Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

2019 ◽  
Vol 15 ◽  
pp. 2473-2485
Author(s):  
Eric W Webb ◽  
Jonathan P Moerdyk ◽  
Kyndra B Sluiter ◽  
Benjamin J Pollock ◽  
Amy L Speelman ◽  
...  
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Undergraduate Research ◽  
Density Functional Theory Calculations ◽  
Molecular Switches ◽  
Photochromic Behavior ◽  
Functional Theory ◽  
Long Wavelength ◽  
H Nmr ◽  
Photoinduced Charge

Our undergraduate research group has long focused on the preparation and investigation of electron-deficient analogs of the perimidinespirohexadienone (PSHD) family of photochromic molecular switches for potential application as "photochromic photooxidants" for gating sensitivity to photoinduced charge transfer. We previously reported the photochemistry of two closely related and more reducible quinazolinespirohexadienones (QSHDs), wherein the naphthalene of the PSHD is replaced with a quinoline. In the present work, we report our investigation of the electrochemistry of these asymmetric QSHDs. In addition to the short wavelength and photochromic long-wavelength isomers, we have found that a second, distinct long-wavelength isomer is produced electrochemically. This different long-wavelength isomer arises from a difference in the regiochemistry of spirocyclic ring-opening. The structures of both long-wavelength isomers were ascertained by cyclic voltammetry and 1H NMR analyses, in concert with computational modeling. These results are compared to those for the symmetric parent PSHD, which due to symmetry possesses only a single possible regioisomer upon either electrochemical or photochemical ring-opening. Density functional theory calculations of bond lengths, bond orders, and molecular orbitals allow the rationalization of this differential photochromic vs electrochromic behavior of the QSHDs.

A Density Functional Theory Study on the Ring-Opening Polymerization of D-Lactide Catalyzed by a Bifunctional-Thiourea Catalyst

2009 ◽  
Vol 62 (2) ◽  
pp. 157 ◽  
Author(s):  
Rong-Xiu Zhu ◽  
Ruo-Xi Wang ◽  
Dong-Ju Zhang ◽  
Cheng-Bu Liu
Keyword(s):  
Density Functional Theory ◽  
Ring Opening ◽  
Density Functional ◽  
Population Analysis ◽  
Density Functional Theory Calculations ◽  
Ring Opening Polymerization ◽  
Acyl Transfer ◽  
Frontier Molecular Orbital ◽  
Functional Theory ◽  
Elimination Pathway

The thiourea-catalyzed methanolysis of d-lactide, a model system for the initiation and propagation of the organocatalyzed ring-opening polymerization (ROP) of lactide, has been studied by performing density functional theory calculations. Both the catalyzed and uncatalyzed reactions are explored along two possible pathways: one involves the stepwise addition–elimination pathway and the other is related to the concerted pathway. It is found that the reaction without the presence of the catalyst is difficult because the barrier involved is as high as 176 kJ mol–1. With the aid of a thiourea catalyst, the barrier is reduced to 88 kJ mol–1 with a preference for the stepwise addition–elimination mechanism over the concerted one. The role of the catalyst has been rationalized by analyzing the frontier molecular orbital interactions between the catalyst and substrates and by performing natural population analysis. Finally, another mechanism involving acyl transfer is discussed for the thiourea-catalyzed ROP.

scholarly journals Assessing the Structure of Octastate Molecular Switches Using 1H NMR Density Functional Theory Calculations

2018 ◽  
Vol 122 (3) ◽  
pp. 1800-1808 ◽  
Author(s):  
Slim Hadj Mohamed ◽  
Jean Quertinmont ◽  
Stéphanie Delbaere ◽  
Lionel Sanguinet ◽  
Benoît Champagne
Keyword(s):  
Density Functional Theory ◽  
1H Nmr ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Molecular Switches ◽  
Functional Theory

A novel nitrogen-containing compound with D-π-A structure: theoretical and experimental study

2014 ◽  
Vol 92 (5) ◽  
pp. 411-416 ◽  
Author(s):  
Xiaoting Gong ◽  
Ziyan Zhou ◽  
Shuguang Zhang ◽  
Shuping Zhuo ◽  
Xiurong Huang ◽  
...  
Keyword(s):  
Density Functional ◽  
Fluorescence Spectra ◽  
Density Functional Theory Calculations ◽  
Absorption And Fluorescence Spectra ◽  
Functional Theory ◽  
H Nmr ◽  
Measured Absorption ◽  
Nmr Techniques ◽  
Good Agreement ◽  
C Nmr

2-(2-Hydroxy-styryl)-4,6-dimethyl-1,3,5-triazine (P1), a novel compound with D-π-A structure, possesses a variety of isomers. Density functional theory calculations were employed to explore the isomerization mechanisms of its various isomers at the 6-311+G** level. The calculated results show that the phenol configurations of compound P1 are more stable than the quinoid configurations, whether they exist as monomers, complexes, with methanol or dimers. The most stable structure of compound P1 was used to calculate the UV-vis and fluorescence spectra. To validate the calculated results, the title compound was synthesized and characterized by 1H NMR and 13C NMR techniques. The measured absorption and fluorescence spectra of P1 in methanol and N,N-dimethylformamide are in good agreement with the calculated ones.

scholarly journals Highly Sterically Encumbered Gold Acyclic Diaminocarbene Complexes: Overriding Electronic Control in Regiodivergent Gold Catalysis

2020 ◽  
Author(s):  
Aaron Ruch ◽  
matthew ellison ◽  
John Nguyen ◽  
Fanji Kong ◽  
Sachin Handa ◽  
...  
Keyword(s):  
Density Functional ◽  
Gold Catalyst ◽  
Density Functional Theory Calculations ◽  
Gold Catalysis ◽  
Functional Theory ◽  
H Nmr ◽  
Nmr Data ◽  
Alkyl Groups ◽  
Out Of Plane ◽  
Acyclic Diaminocarbene

Two series of sterically encumbered gold(I)-acyclic diaminocarbene (ADC) complexes were prepared by reaction of mono- and dialkylamines with gold-bound 2-mesitylphenyl isocyanide (monomesityl series) and 2,6-dimesitylphenyl isocyanide (dimesityl series). X-ray crystal structures and solution <sup>1</sup>H NMR data showed that the ADC-gold complexes adopt major rotameric conformations with the bulky biaryl/terphenyl group and one alkyl group located syn to gold. This engenders substantial steric hindrance at the metal, as evidenced by percent buried volume (%<i>V</i><sub>bur</sub>) parameters of 35.7 – 37.2 for the monomesityl series and 46.4 – 52.4 for the dimesityl series. Modest out-of-plane distortions of the ADC <i>N</i>-substituents in the dimesityl series were attributed to attractive CH···π interactions between alkyl groups and mesityl rings on the basis of dispersion-corrected density functional theory calculations. Gold-catalyzed regiodivergent domino cyclization/hydroarylation reactions of a 1,6-enyne with indole revealed that the bulky biaryl/terphenyl substituents of the ligands exert a strong influence on product selectivity, with the bulkier dimesityl ADC-Au catalysts inducing a shift away from the cyclopropane-fused product toward the normally disfavored alkene product. Incorporation of a yet bulkier bis(2,6-diisopropylphenyl)-substituted terphenyl moiety into the ADC led to a gold catalyst that provided exclusive selectivity for the alkene product. Computational modeling suggested that bulky terphenyl groups hinder attack at the a carbon in the initially formed organogold intermediate, allowing steric effects to override the intrinsic electronic preference for the cyclopropane product.

scholarly journals Highly Sterically Encumbered Gold Acyclic Diaminocarbene Complexes: Overriding Electronic Control in Regiodivergent Gold Catalysis

2020 ◽  
Author(s):  
Aaron Ruch ◽  
matthew ellison ◽  
John Nguyen ◽  
Fanji Kong ◽  
Sachin Handa ◽  
...  
Keyword(s):  
Density Functional ◽  
Gold Catalyst ◽  
Density Functional Theory Calculations ◽  
Gold Catalysis ◽  
Functional Theory ◽  
H Nmr ◽  
Nmr Data ◽  
Alkyl Groups ◽  
Out Of Plane ◽  
Acyclic Diaminocarbene

Two series of sterically encumbered gold(I)-acyclic diaminocarbene (ADC) complexes were prepared by reaction of mono- and dialkylamines with gold-bound 2-mesitylphenyl isocyanide (monomesityl series) and 2,6-dimesitylphenyl isocyanide (dimesityl series). X-ray crystal structures and solution <sup>1</sup>H NMR data showed that the ADC-gold complexes adopt major rotameric conformations with the bulky biaryl/terphenyl group and one alkyl group located syn to gold. This engenders substantial steric hindrance at the metal, as evidenced by percent buried volume (%<i>V</i><sub>bur</sub>) parameters of 35.7 – 37.2 for the monomesityl series and 46.4 – 52.4 for the dimesityl series. Modest out-of-plane distortions of the ADC <i>N</i>-substituents in the dimesityl series were attributed to attractive CH···π interactions between alkyl groups and mesityl rings on the basis of dispersion-corrected density functional theory calculations. Gold-catalyzed regiodivergent domino cyclization/hydroarylation reactions of a 1,6-enyne with indole revealed that the bulky biaryl/terphenyl substituents of the ligands exert a strong influence on product selectivity, with the bulkier dimesityl ADC-Au catalysts inducing a shift away from the cyclopropane-fused product toward the normally disfavored alkene product. Incorporation of a yet bulkier bis(2,6-diisopropylphenyl)-substituted terphenyl moiety into the ADC led to a gold catalyst that provided exclusive selectivity for the alkene product. Computational modeling suggested that bulky terphenyl groups hinder attack at the a carbon in the initially formed organogold intermediate, allowing steric effects to override the intrinsic electronic preference for the cyclopropane product.

scholarly journals Density Functional Theory Studies on the Synthesis of Poly(α-Amino Acid)s Via the Amine-Mediated Ring Opening Polymerizations of N-Carboxyanhydrides and N-Thiocarboxyanhydrides

2021 ◽  
Vol 9 ◽  
Author(s):  
Tianwen Bai ◽  
Botuo Zheng ◽  
Jun Ling
Keyword(s):  
Density Functional Theory ◽  
Amino Acid ◽  
Ring Opening ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
The Past

To synthesize well-defined poly (α-amino acid)s (PAAs), ring opening polymerizations (ROP) of cyclic monomers of α-amino acid N-carboxyanhydrides (NCAs) and N-thiocarboxyanhydrides (NTAs) are most widely used. In this mini-review, we summarize the mechanism details of the monomer preparation and ROP. The present study used density functional theory calculations to reveal the mechanisms together with experimental phenomena in the past decades. Detailed discussion includes normal amine mechanism and the selectivity of the initiators bearing various nucleophilic groups.

Mechanistic insights into the ring-opening of biomass derived lactones

RSC Advances ◽  
2016 ◽  
Vol 6 (16) ◽  
pp. 12932-12942 ◽  
Author(s):  
Shelaka Gupta ◽  
Rishabh Arora ◽  
Nishant Sinha ◽  
Md. Imteyaz Alam ◽  
M. Ali Haider
Keyword(s):  
Density Functional Theory ◽  
Ring Opening ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Ring Opening Reactions ◽  
Oxocarbenium Ion ◽  
Acid Catalyzed

Density functional theory calculations suggest the formation of an oxocarbenium ion intermediate in acid catalyzed ring-opening reactions of biomass derived lactones, which may play an important role in determining it's reactivity.

Regioselectivity and Reactivity of Intramolecular [2+2] Cycloaddition Reactions of Acyl Ketenes: Experimental and Theoretical Studies

Synlett ◽  
2018 ◽  
Vol 29 (14) ◽  
pp. 1836-1841 ◽  
Author(s):  
Mahboobeh Zahedifar ◽  
Hassan Sheibani ◽  
Vahid Saheb
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Cycloaddition Reaction ◽  
Density Functional Theory Calculations ◽  
Theoretical Studies ◽  
Aryl Group ◽  
Functional Theory ◽  
Electron Withdrawing Group ◽  
Experimental And Theoretical Studies ◽  
Mechanism Of The Reaction

The regioselectivity of the intramolecular [2+2] cycloaddition reaction of acyl ketenes formed from metastable mesoionic 1,3-oxazinium-4-olates was investigated by experimental and theoretical methods. The ring opening of the mesoionic N-allyl-2-(2-arylvinyl)-1,3-oxazinium-4-olates led to the formation of unstable acyl ketenes. ­Although there are four possible paths for an intramolecular [2+2] cyclo­addition reaction involving the two double bonds (vinyl and allyl), only the intramolecular [2+2] criss-cross cycloaddition reaction through the vinyl double bond occurred to give 3-allyl-3-azabicyclo[3.1.1]heptane-2,4,6-trione derivatives. These products were not formed when a strongly electron-withdrawing group was present on the aryl group of acrylamides or benzamides. To understand the mechanism of the reaction, density functional theory calculations at the M06-2X/6-31+G(d) level were performed. These revealed that the formation of some preliminary intermediates plays a significant role in the formation of mesoionic 1,3-oxazinium-4-olates.

On the Linear Geometry of Lanthanide Hydroxide (Ln—OH, Ln=La-Lu)

2019 ◽  
Author(s):  
Hassan Harb ◽  
Lee Thompson ◽  
Hrant Hratchian
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Valence Electron ◽  
Density Functional Theory Calculations ◽  
Electron Configuration ◽  
Functional Theory ◽  
Key Species ◽  
Pi Orbitals ◽  
Lanthanide Hydroxide ◽  
Linear Geometry

Lanthanide hydroxides are key species in a variety of catalytic processes and in the preparation of corresponding oxides. This work explores the fundamental structure and bonding of the simplest lanthanide hydroxide, LnOH (Ln=La-Lu), using density functional theory calculations. Interestingly, the calculations predict that all structures of this series will be linear. Furthermore, these results indicate a valence electron configuration featuring an occupied sigma orbital and two occupied pi orbitals for all LnOH compounds, suggesting that the lanthanide-hydroxide bond is best characterized as a covalent triple bond.

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