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Updated: Jul 11, 2025

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV
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Published on: December 29, 2016

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3,4-环基[c]-基中光电子矛盾的起源:一项计算研究

Ganesh Masilamani1, Gamidi Rama Krishna2, Sashi Debnath3

  • 1Department of Chemistry, SRM Institute of Science and Technology, Kattankulathur 603203, India.

Polymers
|November 14, 2023
PubMed
概括

使用16组元素对π合聚合物的原子调系统地改变了光电子特性. 较小的循环替代在基上导致较小的带隙材料与较大的相比.

关键词:
DFT计算方法的计算方法石灰质烯是一种基烯 (chalcogenophene).形态学 形态学 形态学它具有光电子特性.绝缘效应 绝缘效应 绝缘效应

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Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
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Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
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Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
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Isomerism in Complexes
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Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
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