Structural, Spectroscopic, and Reactivity Comparison of Xanthene- and Dibenzofuran-Bridged Cofacial Bisporphyrins

Chang, Christopher J.; Baker, Erin A.; Pistorio, Bradford J.; Deng, Yongqi; Loh, Zhi-Heng; Miller, Scott E.; Carpenter, Scott D.; Nocera, Daniel G.

doi:10.1021/ic0111029

Cited by 97 publications

(111 citation statements)

References 38 publications

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“…[16] Isomer B is more stable and 12.44 kcal mol À1 lower in energy than T. The two isomers display dihedral angles between the two N 4 planes of the pacman ligand at about 708 and 908, respectively. The dihedral angle of B is closer to those in the synthesized binuclear UÀM (M= Mn, Fe, and Co) [25] and MÀM (M= Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Pd, and Cd) [42][43][44][45][46][47][48][49][50]53] complexes . Isomer B contains three types of U À O bonds: two short U=O exo of 1.82 (mean value), two long U À O endo of 2.08 and two even longer U À O endo of 2.13 .…”

Section: Resultsmentioning

confidence: 61%

“…The aryl groups in the macrocycle function as hinges that result in a rigid molecular cleft structure, often called a Pacman structure. [51][52][53] The studies of Arnold et al have shown that this pacman-like macrocylic ligand can accommodate one fivecoordinate uranyl ion in its equatorial plane. [54] However, the second N4 coordination site of the ligand remains metalfree.…”

Section: Introductionmentioning

confidence: 99%

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Binuclear Uranium(VI) Complexes with a “Pacman” Expanded Porphyrin: Computational Evidence for Highly Unusual Bis‐Actinyl Structures

Pan

Shamov

Schreckenbach

2010

Chemistry A European J

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On the basis of uranyl complexes reacting with a polypyrrolic ligand (H(4)L), we explored structures and reaction energies of a series of new binuclear uranium(VI) complexes using relativistic density functional theory. Full geometry optimizations on [(UO(2))(2)(L)], in which two uranyl groups were initially placed into the pacman ligand cavity, led to two minimum-energy structures. These complexes with cation-cation interactions (CCI) exhibit unusual coordination modes of uranyls: one is a T-shaped (T) skeleton formed by two linear uranyls {O(exo)=U(2)=O(endo)-->U(1)(=O(exo))(2)}, and another is a butterfly-like (B) unit with one linear uranyl coordinating side-by-side to a second cis-uranyl. The CCI in T was confirmed by the calculated longest distance and lowest stretching vibrational frequency of U(2)=O(endo) among the four U=O bonds. Isomer B is more stable than T, for which experimental tetrameric analogues are known. The formation of B and T complexes from the mononuclear [(UO(2))(H(2)L)(thf)] (M) was found to be endothermic. The further protonation and dehydration of B and T are thermodynamically favorable. As a possible product, we have found a trianglelike binuclear uranium(VI) complex having a O=U=O=U=O unit.

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Section: Resultsmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Binuclear Uranium(VI) Complexes with a “Pacman” Expanded Porphyrin: Computational Evidence for Highly Unusual Bis‐Actinyl Structures

Pan

Shamov

Schreckenbach

2010

Chemistry A European J

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“…17 The DPD spacer engenders clefts with dimensions of ∼7.5 Å, whereas the DPX gives a cleft dimension of ∼4 Å. 18 We note, however, that the DPD framework itself is extremely flexible and is able to span large vertical dimension. The metal-metal distances of DPD can range from 3.504 Å for Fe 2 O(DPD), which clamps its Pacman bite around a bridging oxo ligand, to 7.775 Å for Zn 2 -(DPD), 19 which allows the DPD platform to attain its natural splayed conformation.…”

Section: Xanthene-and Dibenzofuran-bridged Pacman Assembliesmentioning

confidence: 85%

Role of Proton‐Coupled Electron Transfer in O—O Bond Activation

Rosenthal

Nocera

2007

ChemInform

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The selective reduction of oxygen to water requires four electrons and four protons. The design of catalysts that promote oxygen reduction therefore requires the management of both electron and proton inventories. Pacman and Hangman porphyrins provide a cleft for oxygen binding, a redox shuttle for oxygen reduction, and functionality for tuning the acid-base properties of bound oxygen and its intermediates. With proper control of the proton-coupled electron transfer events, O-O bond breaking of oxygen, and more generally oxygenated substrates, may be achieved with high efficiencies. The rule set developed for oxygen reduction may be applied to a variety of other small molecule activation reactions of consequence to energy conversion.

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“…For systems such as the copper -copper dibenzofuran-bridged co-facial bisporphyrins 30 and 31 EPR spectroscopy has been shown to be an essential analytical tool that provides information not available from optical studies. It also complements crystallographic studies by probing intramolecular metal-metal arrangements in frozen solution (Chang et al 2002). <Chemical Structure 14> Mixed cyclization of porphyrin containing phthalonitrile compounds with an europium(III) halfsandwich phthalocyanine complex in the presence DBU gave a series of porphyrin-appended europium(III)bis(phthalocyaninato)complexes.…”

Section: Heteroligand Systemsmentioning

confidence: 94%