Luminescent closed shell nickel(ii) pyridyl-azo-oximates and the open shell anion radical congener: molecular and electronic structure, ligand redox behaviour and biological activity

ABSTRACT: The influence of a redox-active ligand on spin changing events induced by coordination of exogenous donors is investigated within the cobalt complex [CoII(DPP•2‒)], bearing a redox-active DPP2‒ ligand (DPP = dipyrrin-bis-(o,p-di-tert-butylphenolato) with a pentafluorophenyl moiety on the meso-position. This square planar complex was subjected to coordination of THF, pyridine, tBuNH2 and AdNH2 (Ad = 1‑adamantyl), and the resulting complexes were analyzed with a variety of experimental (XRD, NMR, UV-Vis, HRMS, SQUID, Evans’ method) and computational (DFT, NEVPT2-CASSCF) techniques to elucidate the respective structures, spin states and orbital compositions of the corresponding octahedral bis-donor adducts, relative to [CoII(DPP•2‒)]. This starting species is best described as an open-shell singlet complex containing a DPP•2‒ ligand radical that is antiferromagnetically coupled to a low-spin (S = ½) cobalt(II) center. The redox-active DPPn‒ ligand plays a crucial role in stabilizing this complex, and in its facile conversion to the triplet THF-adduct [CoII(DPP•2‒)(THF)2] and closed-shell singlet pyridine and amine adducts [CoIII(DPP3‒)(L)2] (L = py, tBuNH2 or AdNH2). Coordination of the weak donor THF to [CoII(DPP•2-)] changes the orbital overlap between the DPP•2‒ ligand radical π-orbitals and the cobalt(II) metalloradical d-orbitals, which results in a spin-flip to the triplet ground state without changing the oxidation states of the metal or DPP•2‒ ligand. In contrast, coordination of the stronger donors pyridine, tBuNH2 or AdNH2 induces metal-to-ligand single-electron transfer, resulting in formation of low-spin (S = 0) cobalt(III)-complexes [CoIII(DPP3‒)(L)2] containing a fully reduced DPP3‒ ligand, thus explaining their closed-shell singlet electronic ground states.

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A new family of [IrCl5(NO)]-salts. Structural diversity tuned by aryl embraces

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314093504 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C649-C649

Author(s):

Florencia Di Salvo ◽

Ana Foi ◽

Ricardo Baggio ◽

Damian Bikiel ◽

Fabio Doctorovich

Keyword(s):

Electronic Structure ◽

Structural Diversity ◽

Closed Shell ◽

Open Shell ◽

Phosphonium Salts ◽

Structural Behaviour ◽

Interaction Domain ◽

Theoretical Evaluation ◽

New Family ◽

Electronic Distribution

The interactions experimented by multiple phenyl or other aromatic groups in crystals have been described as ``embraces'' since 1995, when Dance and co-workers developed the embrace paradigm as an important and widespread tool of supramolecular chemistry. There are three main classes of Multiple Phenyl Embraces (MPE) depending on the total number of phenyl rings (Ph) located in the interaction domain: sextuple (6PE), quadruple (4PE), and double phenyl embrace (2PE) [1]. Recently, an accurate theoretical evaluation of the MPE motifs between PPh4+was presented by Novoa et al [2]. In our laboratory we demonstrated that by changing the counterion of the [IrCl5(NO)]-salts from K+to PPh4+, it was possible to stabilize an excited state of the metal complex anion. The electronic distribution of the IrNO moiety in K[IrCl5(NO)] can be depicted as the closed-shell electronic structure IrIII–NO+. However, in PPh4[IrCl5(NO)] an unprecedented electronic perturbation takes place favouring the open-shell electronic structure IrIv–NO* [3]. These results together with the interesting systematic studies on MPE, encouraged us to explore the synthesis of new phosphonium salts. In this work we report new phosphonium ions of the type Ph3PR+and five new Ph3PR[IrCl5(NO)] salts (R = aryl, methylaryl). Structural analyses of these compounds were done in the context of the multiple embraces motifs. For the new unsymmetrical [IrCl5(NO)]-salts, the supramolecular arrangements are different from the one observed for the PPh4+one. In the last one, the 4PE infinite chains run parallel to the columns described by the anions [3] and for the others, the presence of bulkier substituents give place to symmetries that favours other kinds of aryl embraces resulting in a side by side location of the anions. Finally, DFT calculations were performed to evaluate the theoretical concerns regarding the structural behaviour, as well as the electronic distribution along the family of compounds.

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Evolution of the electronic structure in open-shell donor-acceptor organic semiconductors

Nature Communications ◽

10.1038/s41467-021-26173-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Zhongxin Chen ◽

Wenqiang Li ◽

Md Abdus Sabuj ◽

Yuan Li ◽

Weiya Zhu ◽

...

Keyword(s):

Electronic Structure ◽

Organic Semiconductors ◽

High Performance ◽

Closed Shell ◽

Open Shell ◽

Ground State Structure ◽

Structure Property ◽

System A ◽

Diradical Character ◽

Donor Acceptor

AbstractMost organic semiconductors have closed-shell electronic structures, however, studies have revealed open-shell character emanating from design paradigms such as narrowing the bandgap and controlling the quinoidal-aromatic resonance of the π-system. A fundamental challenge is understanding and identifying the molecular and electronic basis for the transition from a closed- to open-shell electronic structure and connecting the physicochemical properties with (opto)electronic functionality. Here, we report donor-acceptor organic semiconductors comprised of diketopyrrolopyrrole and naphthobisthiadiazole acceptors and various electron-rich donors commonly utilized in constructing high-performance organic semiconductors. Nuclear magnetic resonance, electron spin resonance, magnetic susceptibility measurements, single-crystal X-ray studies, and computational investigations connect the bandgap, π-extension, structural, and electronic features with the emergence of various degrees of diradical character. This work systematically demonstrates the widespread diradical character in the classical donor-acceptor organic semiconductors and provides distinctive insights into their ground state structure-property relationship.

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Reactivities of singlet oxygen: open-shell or closed-shell?

Physical Chemistry Chemical Physics ◽

10.1039/d0cp02466j ◽

2020 ◽

Vol 22 (24) ◽

pp. 13373-13377

Author(s):

Zexing Qu

Keyword(s):

Electronic Structure ◽

Singlet Oxygen ◽

Closed Shell ◽

Open Shell

The electronic structure and the reactivity of singlet oxygen with respect to two typical reactions.

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Molecular and electronic structure of nonradical homoleptic pyridyl-azo-oxime complexes of cobalt(iii) and the azo-oxime anion radical congener: an experimental and theoretical investigation

Dalton Transactions ◽

10.1039/c3dt53460j ◽

2014 ◽

Vol 43 (14) ◽

pp. 5317-5334 ◽

Cited By ~ 10

Author(s):

Shuvam Pramanik ◽

Sima Roy ◽

Tapas Ghorui ◽

Sanjib Ganguly ◽

Kausikisankar Pramanik

Keyword(s):

Electronic Structure ◽

Theoretical Investigation ◽

Anion Radical ◽

Molecular And Electronic Structure

Synthesis and optoelectronic study of Co(iii)–pyridyl-azo-oxime complexes and isolation of Co(iii)-bound azo-oxime anion radical.

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Ligand-Mediated Spin State Changes in a Cobalt-Dipyrrin-Bisphenol Complex

10.26434/chemrxiv.12605333 ◽

2020 ◽

Author(s):

Nicolaas P. van Leest ◽

Wowa Stroek ◽

Maxime A. Siegler ◽

Jarl Ivar van der Vlugt ◽

Bas de Bruin

Keyword(s):

Cobalt Complex ◽

Closed Shell ◽

Open Shell ◽

Triplet Ground State ◽

Redox Active Ligand ◽

Redox Active ◽

Square Planar ◽

Amine Adducts ◽

Meso Position ◽

Electronic Ground

ABSTRACT: The influence of a redox-active ligand on spin changing events induced by coordination of exogenous donors is investigated within the cobalt complex [CoII(DPP•2‒)], bearing a redox-active DPP2‒ ligand (DPP = dipyrrin-bis-(o,p-di-tert-butylphenolato) with a pentafluorophenyl moiety on the meso-position. This square planar complex was subjected to coordination of THF, pyridine, tBuNH2 and AdNH2 (Ad = 1‑adamantyl), and the resulting complexes were analyzed with a variety of experimental (XRD, NMR, UV-Vis, HRMS, SQUID, Evans’ method) and computational (DFT, NEVPT2-CASSCF) techniques to elucidate the respective structures, spin states and orbital compositions of the corresponding octahedral bis-donor adducts, relative to [CoII(DPP•2‒)]. This starting species is best described as an open-shell singlet complex containing a DPP•2‒ ligand radical that is antiferromagnetically coupled to a low-spin (S = ½) cobalt(II) center. The redox-active DPPn‒ ligand plays a crucial role in stabilizing this complex, and in its facile conversion to the triplet THF-adduct [CoII(DPP•2‒)(THF)2] and closed-shell singlet pyridine and amine adducts [CoIII(DPP3‒)(L)2] (L = py, tBuNH2 or AdNH2). Coordination of the weak donor THF to [CoII(DPP•2-)] changes the orbital overlap between the DPP•2‒ ligand radical π-orbitals and the cobalt(II) metalloradical d-orbitals, which results in a spin-flip to the triplet ground state without changing the oxidation states of the metal or DPP•2‒ ligand. In contrast, coordination of the stronger donors pyridine, tBuNH2 or AdNH2 induces metal-to-ligand single-electron transfer, resulting in formation of low-spin (S = 0) cobalt(III)-complexes [CoIII(DPP3‒)(L)2] containing a fully reduced DPP3‒ ligand, thus explaining their closed-shell singlet electronic ground states.

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Electronic Structure Calculations of the Copper Oxygen Planes in Yba2Cu3O6+δ, for 0 < δ < 1

MRS Proceedings ◽

10.1557/proc-169-37 ◽

1989 ◽

Vol 169 ◽

Author(s):

J. A. Cogordan

Keyword(s):

Electronic Structure ◽

Excited State ◽

Ab Initio ◽

Molecular Orbital ◽

Lower Energy ◽

Closed Shell ◽

Electronic Structure Calculations ◽

Open Shell ◽

Molecular Orbitals ◽

Structure Calculations

AbstractMolecular ab initio seIf-consistent calculations on clusters simulating the copper-oxygen layers in the Yba2Cu3O6;δ are reported. The electronic structure, of this layer, was computed for different sets of values of the lattice parameters (a,b,c), according to their dependence on the oxygen stiochiometry. For the molecular orbitals , two different electronic occupations are considered, a closed shell and an open shell. For the open shell, an electron has been excited to the first virtual molecular orbital. It is found that this excited state has lower energy than the closed shell configuration for 0 < δ < 1. Molecular energies an electronic population are reported.

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