EPR Hyperfine Structures of Cation and Anion Radicals of Triafulvalene, Pentafulvalene and Heptafulvalene; A Theoretical Study

Abstract

In this study, the EPR hyperfine coupling constants and spin densities of cation and anion radicals of triafulvalene, pentafulvalene and heptafulvalene were calculated by using DFT method with B3LYP functional at LanL2DZ level. The hyperfine structures formed EPR spectra of all the cation and anion radicals were determined. It was seen that in the cation cases of triafulvalene and heptafulvalene spin density is delocalized throughout the molecule whereas in their anion cases it is essentially localized on only a single ring. The reason of this distribution of the unpaired spin was investigated by their Natural Bond Orbital (NBO) and Mullikan charge analyses. These analyses showed that in the anion cases of the molecules the interaction energies between the interring C-C bond and the ring C-C bonds are different for both the two rings and one of them is quite higher than the other. The simulated EPR spectra obtained by EPR Simulator software program were harmoniously given with together their experimental spectra.

Keywords

• Fulvalene
• Hyperfine splitting
• EPR
• DFT
• Simulation

Triafulvalen, Pentafulvalen ve Heptafulvalenin Katyon ve Anyon Radikallerinin EPR Aşırı İnce-yapı Yapıları: Bir Teorik Çalışma

Abstract

Bu çalışmada triafulvalen, pentafulvalen ve heptafulvalen moleküllerinin katyon ve anyon radikallerinin EPR aşırı ince-yapı çiftlenim sabitleri ve spin yoğunlukları, B3LYP fonksiyonelli DFT ile LanL2DZ seviyesinde hesaplandı. Bütün katyon ve anyon radikallerinin EPR spektrumlarını oluşturan aşırı ince-yapı yapıları belirlendi. Triafulvalen ve heptafulvalenin anyon durumlarında spin yoğunluğu, hemen hemen yalnızca tekil bir halka üzerinde bulunurken onların katyon durumlarında bütün bir molekül üzerinde dağılmış olarak gözlendi. Çiftlenmemiş spinin bu dağılımının nedeni, onların Doğal Bağ Orbital (NBO) ve Mulliken yük analizleri ile araştırıldı. Bu analizler, moleküllerin anyon durumlarında halkalar arası C-C bağının halka C-C bağları arasındaki etkileşme enerjilerini her iki halka için farklı ve birini diğerine kıyasla oldukça yüksek gösterdi. EPR Simulator yazılım programı ile elde edilmiş simülasyon EPR spektrumları, deneysel spektrumlarla birlikte uyum içerisinde verildi.

Keywords

• Fulvalene
• İnceyapı yarılması
• EPR
• DFT
• Simülasyon

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