Conformational effects on high-spin organic molecules
摘要:
The ability of m-phenylene to ferromagnetically couple spin-containing substituents that are substantially twisted out of conjugation is investigated. The ''bis(TMM)'' strategy is employed, in which two triplet TMM biradicals am linked through m-phenylene to produce relatively stable, organic tetraradicals that are characterized by EPR spectroscopy. Under conditions of moderate twisting (4), ferromagnetic coupling is seen, and the tetraradical has a quintet ground state. Severely twisting both TMMs as in 13 disrupts spin communication, and two noninteracting triplets are produced. This is in contrast to other highly twisted m-phenylene derivatives, in which antiferromagnetic coupling has been observed. Surprisingly, severely twisting only one TMM (14) still produces ferromagnetic coupling and a quintet ground state through a spin polarization mechanism analogous to that proposed for 90-degrees twisted ethylene. Several ring-constrained TMMs (17-19) are investigated as models for mom nearly planar systems.
Conformational effects on high-spin organic molecules
摘要:
The ability of m-phenylene to ferromagnetically couple spin-containing substituents that are substantially twisted out of conjugation is investigated. The ''bis(TMM)'' strategy is employed, in which two triplet TMM biradicals am linked through m-phenylene to produce relatively stable, organic tetraradicals that are characterized by EPR spectroscopy. Under conditions of moderate twisting (4), ferromagnetic coupling is seen, and the tetraradical has a quintet ground state. Severely twisting both TMMs as in 13 disrupts spin communication, and two noninteracting triplets are produced. This is in contrast to other highly twisted m-phenylene derivatives, in which antiferromagnetic coupling has been observed. Surprisingly, severely twisting only one TMM (14) still produces ferromagnetic coupling and a quintet ground state through a spin polarization mechanism analogous to that proposed for 90-degrees twisted ethylene. Several ring-constrained TMMs (17-19) are investigated as models for mom nearly planar systems.
Bicyclic bridged metallocene compounds and polymers produced therefrom
申请人:Chevron Phillips Chemical Company LP
公开号:US09758600B1
公开(公告)日:2017-09-12
Disclosed herein are catalyst compositions containing bicyclic bridged metallocene compounds. These catalyst compositions can be used for the polymerization of olefins. For example, ethylene polymers produced using these catalyst compositions can be characterized by low molecular weights and high melt flow rates, and can be produced without the addition of hydrogen.
A Practical and General Diels–Alder Reaction of Pentafulvenes with Arynes
作者:Sachin Suresh Bhojgude、Trinadh Kaicharla、Anup Bhunia、Akkattu T. Biju
DOI:10.1021/ol301742k
日期:2012.8.17
A high-yielding, versatile and practical Diels-Alder reaction of pentafulvenes with arynes under mild reaction conditions is reported. The aryne generated by the fluoride induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates undergoes efficient cycloaddition with 6-substituted and 6,6-disubstituted pentafulvenes leading to the formation of benzonorbornadiene derivatives.