Variable Nitric Oxide Reactivity of Tropocoronand Cobalt(III) Nitrite Complexes as a Function of the Polymethylene Linker Chain Length

Kozhukh, Julia; Lippard, Stephen J.

doi:10.1021/ic3012266

Cited by 4 publications

(2 citation statements)

References 31 publications

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“…Whereas [Co(TC-3,3)(NO)] was reported to be paramagnetic, the analogous TC-4,4 and TC-5,5 complexes are diamagnetic, a more common situation for {CoNO} 8 complexes . The hypothetical [Co(TC-6,6)(NO)] complex has thus far eluded isolation and characterization …”

Section: Introductionmentioning

confidence: 99%

Singlet–Triplet Gaps of Cobalt Nitrosyls: Insights from Tropocoronand Complexes

et al. 2015

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A DFT study of cobalt-nitrosyl [n,n]tropocoronand (TC-n,n) complexes has revealed a sharp reduction of singlet-triplet gaps as the structures change from near-square-pyramidal 10 (for n = 3) to trigonal-bipyramidal with an equatorial NO (for n = 5, 6). For n = 6, low-energy triplet states may result in enhanced reactivity, which would account for the failure to isolate [Co(TC-6,6)(NO)] as a stable species. reinvestigation of the molecule. The calculations also revealed a decreasing singlet-triplet gap and low-energy triplet states as the coordination geometry changed from the nearly SQP TC-3,3 complex to the TBP TC-5,5 and TC-6,6 complexes. Thermally accessible triplet states are a distinct possibility for 6,6)(NO)], which would explain its apparent instability. The lowest-energy singlet and triplet states of the [Co(TCn,n)(NO)] complexes (n = 3-6) were optimized with the B3LYP, OLYP, and PW91 functionals and the 6-311G(d,p) basis set. In general, the hybrid functional B3LYP led to a broken-symmetry 45 M S = 0 solution as the ground state, whereas the pure functionals Scheme 1. Dianion of an [n,n]tropocoronand (n,n-TC) ligand.PW91 and OLYP led to closed-shell ground states. Interestingly, 50 depending on the starting point of the optimizations, two distinct triplet states, denoted T 1 and T 2 in the discussion below, could be obtained. The T 1 state may be described as low-spin S = ½ Co(II) ferromagnetically coupled to a NO radical, and the T 2 state may as a high-spin S = 2 Co(III) antiferromagnetically coupled to an S 55 = 1 NO -anion. Table 1

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Section: Introductionmentioning

confidence: 99%

Singlet–Triplet Gaps of Cobalt Nitrosyls: Insights from Tropocoronand Complexes

et al. 2015

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“… 15 These species exist in square-planar or distorted square-planar geometries, with twist angles, defined as the angle between planes formed by the metal and the two sets of aminotroponeiminate nitrogen atoms, of 8° and 41° for the four-coordinate complexes. 15 In our pursuit to examine the size dependence of cobalt(II) and cobalt(III) tropocoronands on their ability to tune reactivity with nitric oxide, 16 , 17 we prepared and structurally characterized two pseudotetrahedral cobalt(III) complexes, [Co(TC-5,5)](BF 4 ) and [Co(TC-6,6)](BPh 4 ). Their syntheses and properties are described here.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Mononuclear, Pseudotetrahedral Cobalt(III) Compounds

2014

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The preparation and characterization of two mononuclear cobalt(III) tropocoronand complexes, [Co(TC-5,5)](BF4) and [Co(TC-6,6)](BPh4), are reported. The cobalt(III) centers exist in rare pseudotetrahedral conformations, with twist angles of 65° and 74° for the [Co(TC-5,5]+ and [Co(TC-6,6)]+ species, respectively. Structural and electrochemical characteristics are compared with those of newly synthesized [Ga(TC-5,5)](GaCl4) and [Ga(TC-6,6)](GaCl4) analogues. The spin state of the pseudotetrahedral [Co(TC-6,6)](BPh4) compound was determined to be S = 2, a change in spin state from the value of S = 1 that occurs in the square-planar and distorted square-planar complexes, [Co(TC-3,3)](X) (X = BPh4, BAr′4) and [Co(TC-4,4)](BPh4), respectively.

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A cobalt–nitrosyl complex with a hindered hydrotris(pyrazolyl)borate coligand: detailed electronic structure, and reactivity towards dioxygen

et al. 2017

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The cobalt-nitrosyl complex [Co(NO)(L3)] is supported by a highly hindered tridentate nitrogen ligand, hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate (denoted as L3), and shows a linear Co-N-O unit. This complex was prepared by the reaction of the potassium salt of L3 with the cobalt-nitrosyl precursor [Co(NO)(tmeda)](BPh) (tmeda = N,N,N,'N'-tetramethylethylenediamine). The obtained cobalt-nitrosyl complex as well as the corresponding products from the reaction with dioxygen, [Co(η-ON)(L3)] and [Co(η-ONO)(L3)], were characterised by X-ray crystallography and a number of spectroscopic methods including IR/far-IR, UV-Vis, and NMR spectroscopy. We also performed MCD measurements and DFT calculations to further elucidate the electronic structure of [Co(NO)(L3)] and the optical properties of the complex. The MCD spectra reveal two NO-to-Co charge-transfer transitions with strong excited state displacements that give rise to vibrational progressions in the MCD spectra, indicative of a very covalent Co-NO bond. These results provide new insight into the properties of the Co-NO bond and the electron distribution in the complex, which is best described as [Co(NO)(L3)].

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Variable Nitric Oxide Reactivity of Tropocoronand Cobalt(III) Nitrite Complexes as a Function of the Polymethylene Linker Chain Length

Cited by 4 publications

References 31 publications

Singlet–Triplet Gaps of Cobalt Nitrosyls: Insights from Tropocoronand Complexes

Singlet–Triplet Gaps of Cobalt Nitrosyls: Insights from Tropocoronand Complexes

Synthesis and Characterization of Mononuclear, Pseudotetrahedral Cobalt(III) Compounds

A cobalt–nitrosyl complex with a hindered hydrotris(pyrazolyl)borate coligand: detailed electronic structure, and reactivity towards dioxygen

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