Konsequenzen der Triplett‐Aromatizität in 4nπ‐Elektronen‐Annulenen – die Berechnung magnetischer Abschirmungen für offenkettige Moleküle

  title={Konsequenzen der Triplett‐Aromatizit{\"a}t in 4n$\pi$‐Elektronen‐Annulenen – die Berechnung magnetischer Abschirmungen f{\"u}r offenkettige Molek{\"u}le},
  author={Valentin Gogonea and Paul von Ragu{\'e} Schleyer and Peter R. Schreiner},
  journal={Angewandte Chemie},
Die Triplettzustande von 4nπ-Elektronen-Annulenen sollten, wie Baird 1972 vorgeschlagen hatte, eher als aromatisch denn als antiaromatisch betrachtet werden. Diese Triplettzustande haben planare, symmetrische Geometrien (wie bei C9H9+, siehe rechts), viel niedrigere Energien als die entsprechenden Triplett-Referenzzustande und weisen nach Rechnungen, in denen die Wechselwirkungen mit den ungepaarten Elektronen vernachlassigt werden, diatrope Ringstrome auf (kernunabhangige chemische… Expand
44 Citations
A preferred disrotatory 4n electron Möbius aromatic transition state for a thermal electrocyclic reaction.
Not forbidden: Thermal 4n electron electrocyclic reactions of Hückel topology structures proceed via "allowed" conrotatory pathways. However, for a Möbius topology, the Woodward-Hoffmann rules may beExpand
Curved aromaticity of a corannulene-based neutral radical: crystal structure and 3 d unbalanced delocalization of spin.
2. 2002–2003年大阪大学英文研究年報(Annual Report)論文100選 受 賞 題 目 : A New Trend in Phenalenyl Chemistry: A Persistent Neutral Radical, 2,5,8-Tri-tert-butyl-1,3-Diazaphenalenyl, and the Excited Triplet State ofExpand
Reversal of Orbital Symmetry Control in Electrocyclic Ring Closures through Craig-Möbius Aromaticity.
  • M. Mauksch, S. Tsogoeva
  • Chemistry, Medicine
  • Chemphyschem : a European journal of chemical physics and physical chemistry
  • 2016
Experimentalists are challenged to find the organometallic thermal electrocyclizations that are computationally predicted to proceed with opposite stereoselectivity compared to their metal-freeExpand
Triplet-state aromaticity of 4npi-electron monocycles: analysis of bifurcation in the pi contribution to the electron localization function.
The pi contribution to the electron localization function (ELF) is used to compare 4npi- and (4n+2)pi-electron annulenes, with particular focus on the aromaticity of 4npi-electron annulenes in theirExpand
Scope and limitations of Baird's theory on triplet state aromaticity: application to the tuning of singlet-triplet energy gaps in fulvenes.
It is shown that the singlet-triplet energy gaps of pentafulvenes are easily varied through substitution by as much as 36 kcal mol(-1) and that triplet-state aromaticity can greatly influence the properties of conjugated compounds in the T1 state. Expand
The phenalenyl motif: a magnetic chameleon.
The 12pi cation (3) and 14pi anion (4) derived from the phenalenyl radical (2) support diatropic ("aromatic") perimeter ring currents, but isoelectronic replacement of the central atom by eitherExpand
Demonstration of "Möbius" aromaticity in planar metallacycles.
This work reports the first computationally confirmed 4npi aromatic planar metallacyclic examples and their building principles, and the role of wave function boundary conditions (periodic vs. antiperiodic) in chemistry is further stressed. Expand
Neutral Möbius Aromatics: Derivatives of the Pyrrole Congener Aza[11]annulene as Promising Synthetic Targets†
Amino- and methyl-disubstituted derivatives of an aromatic 12π electron pyrrole homologue Mobius 1H-aza[11]annulene are predicted computationally at the B3LYP/6-31G* level of theory to be distinctlyExpand
Analysis of a Compound Class with Triplet States Stabilized by Potentially Baird Aromatic [10]Annulenyl Dicationic Rings.
The low-lying triplet state of a recently published compound (TMTQ) was analyzed quantum chemically in light of suggestions that it is influenced by Baird aromaticity, and it is found that TMTQ and its analogues are Hückel-Baird hybrids allowing for tuning between closed-shell 4n+2 HüCkel aromaticity and open- shell 4n Baird aromaticality. Expand
Magnetic Shielding, Aromaticity, Antiaromaticity and Bonding in the Low-Lying Electronic States of S2 N2.
The results strongly suggest that S2 N2 is the first example of an inorganic ring for which theory predicts substantial changes in aromaticity upon vertical transition from the ground state to the first singlet excited or lowest triplet electronic states. Expand


Transition-State Spectroscopy of Cyclooctatetraene
The photoelectron spectrum shows that the singlet lies well below the triplet in D8h COT and confirms ab initio predictions that the molecule violates Hund's rule. Expand
Ab initio study of cyclobutadiene in excited states: optimized geometries, electronic transitions and aromaticities
Abstract An Ab initio SCF-CI study of planar cyclobutadiene (CB) in ground and excited states has been carried out. The equilibrium geometries of some valence and Rydberg states have been calculated,Expand
Density-functional thermochemistry. III. The role of exact exchange
Despite the remarkable thermochemical accuracy of Kohn–Sham density‐functional theories with gradient corrections for exchange‐correlation [see, for example, A. D. Becke, J. Chem. Phys. 96, 2155Expand
A multireference coupled‐cluster study of the ground state and lowest excited states of cyclobutadiene
The electronic structure of the ground state and several low‐lying excited states of cyclobutadiene are studied using the new state‐universal multireference coupled‐cluster method with single andExpand
Violations of Hund's rule in molecules — where to look for them and how to identify them
Abstract Violations of Hund's rule are predicted to be found in D 4 h cyclobutadiene (CBD), D 8 h cyclooctatetraene (COT), and in non-Kekule hydrocarbon diradicals that have disjoint NBMOs. In D 4 hExpand
Nucleus-Independent Chemical Shifts:  A Simple and Efficient Aromaticity Probe.
The use of absolute magnetic shieldings, computed at ring centers with available quantum mechanics programs, are proposed as a new aromaticity/antiaromaticity criterion to establish NICS as an effective aromaticity criterion. Expand
Geometry of triplets and dianions of aromatic and antiaromatic systems
Abstract The nodal properties of orbitals are used as guidelines for changes of geometry in excited states. Similarities in structure for the lowest triplet and the dianion are explained.Expand
Aromaticity-Based Theory of Pericyclic Reactions
The resonance energies of conjugated compounds in the electronically excited state were calculated on the basis of the aromaticity theory previously reported by us. The allowednesses of pericyclicExpand
Experimental and Computational Studies of the Structures and Energetics of Cyclooctatetraene and Its Derivatives
Conformational changes in cyclooctatetraene (COT) and its substituted derivatives have been the subject of considerable interest for several decades.1,2 Relatively little is known, however, about theExpand
Computational Study of the Thermochemistry of C5H5+ Isomers: Which C5H5+ Isomer Is the Most Stable?
G2, G2(MP2), and G2(B3LYP/MP2/CC) calculations show the vinylcyclopropenyl cation 3 to be the lowest energy of the C5H5+ isomers. The calculated energy difference between the cyclopentadienyl cationExpand