Ferrocene鈥揇ithiolene Hybrids: Control of Strong Donor鈥揂cceptor Electronic Communication to Reverse the Charge Transfer Direction

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• 作者：Tetsuro Kusamoto ; Kenji Takada ; Ryota Sakamoto ; Shoko Kume ; Hiroshi Nishihara
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：November 19, 2012
• 年：2012
• 卷：51
• 期：22
• 页码：12102-12113
• 全文大小：582K
• 年卷期：v.51,no.22(November 19, 2012)
• ISSN：1520-510X

文摘

We prepared a novel class of ferrocene鈥揹ithiolene hybrid molecules, FcS₄dt(Me)₂ and FcS₄dt[Pt(^tBu₂bpy)] (where FcS₄dt indicates 2-(1,3-dithia[3]ferrocenophane-2-ylidene)-1,3-dithiole-4,5-dithiolate and ^tBu₂bpy indicates 4,4鈥?di-tert-butyl-2,2鈥?bipyridine), in which the ferrocene moiety was bound to the planar conjugated dithiolene skeleton via two sulfur atoms such that the cyclopentadienyl rings were perpendicular to the dithiolene backbone. The physical properties and electronic structures of the complexes and their oxidized species [FcS₄dt(Me)₂]^鈥? and [FcS₄dt[Pt(^tBu₂bpy)]]^鈥? were investigated by means of single-crystal X-ray diffraction (XRD) analysis, cyclic voltammetry, electron paramagnetic resonance (EPR), and UV鈥搗is near infrared (UV鈥搗is鈥揘IR) spectroscopy. The electron density distributions of the highest occupied molecular orbitals (HOMOs) of FcS₄dt(Me)₂ and FcS₄dt[Pt(^tBu₂bpy)] differed remarkably in that the HOMO of the former was ferrocene-based whereas that of the latter was dithiolene-based. The differences in the HOMO distributions originated from the energy level of the dithiolene-based 蟺-orbital in each of the complexes, which was controlled by changing R in FcS₄dt(R)₂ (R = Me for FcS₄dt(Me)₂; 2R = Pt(^tBu₂bpy) for FcS₄dt[Pt(^tBu₂bpy)]). We succeeded in analyzing the crystal structure of [FcS₄dt[Pt(^tBu₂bpy)]](F₄TCNQ)路C₆H₁₄路CH₂Cl₂ (where F₄TCNQ indicates 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), which provided a rare example of the crystal structure of a [Pt(diimine)(dithiolate)]^鈥? ion-based complex. A comparison of the bond lengths in FcS₄dt[Pt(^tBu₂bpy)] and [FcS₄dt[Pt(^tBu₂bpy)]]^鈥? suggested that the latter complex displayed a conjugated dithiolene-based 蟺-radical character. These considerations agreed well with the electronic structures calculated using density functional theory (DFT) and time-dependent(TD)-DFT methods. Significant electronic communication between the ferrocene and dithiolene moieties was detected for both [FcS₄dt(Me)₂]^鈥? and [FcS₄dt[Pt(^tBu₂bpy)]]^鈥? in the appearance of an intramolecular charge transfer band, which was hardly observed for previously reported ferrocene鈥揹ithiolene hybrid molecules. The charge transfer direction was reversed between the two cations. The electron coupling parameter H_AB and the potential energy curves of the oxidized complexes were estimated based on the classical two-state Marcus鈥揌ush theory. These results suggest that FcS₄dt-based metalladithiolenes can exhibit controllable electronic structures expressed as double-minimum potential energy curves.