Unusual attractive interactions between selenium and oxygen in selenoiminoquinones

Barton, Derek H. R.; Hall, Michael B.; Lin, Zuzhang; Parekh, Shyamal I.; Reibenspies, Joseph

doi:10.1021/ja00065a015

Cited by 97 publications

(101 citation statements)

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“…The orientational effect of p-YC 6 H 4 (Ar) on d(Se) is elucidated for ArSeR, based on experimental and theoretical investigations. The effect is examined in the cases in which SeÀC R in ArSeR is either in the Ar plane (pl) or is perpendicular to the plane (pd).…”

Section: Introductionmentioning

confidence: 99%

“…Contributions of each molecular orbital and each transition on s nisms must also be important when the structures are discussed based on the observed values. We have been much interested in the orientational effect on d(Se) in p-YC 6 H 4 SeR (ArSeR), together with the mechanism. We have already pointed out the importance of the effect for the better interpretation of d (Se) of ArSeR in a uniform manner.…”

Section: Introductionmentioning

confidence: 99%

“…To understand the orientational effect based on the theoretical background, quantum chemical (QC) calculations were performed on ArSeH (4), ArSeMe (5), and ArSePh (6). The conformations were fixed to pl and pd in the calculations.…”

Section: Introductionmentioning

confidence: 99%

“…The measurements of d (Se) are necessary to understand based on plain rules founded on the theoretical background. A charge-transfer mechanism has been proposed to explain the downfield shift by the neighboring oxygen atom [6] and it is demonstrated that the mechanism plays an important role in weak interactions.…”

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confidence: 99%

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Orientational Effect of Aryl Groups on ⁷⁷Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Nakanishi

Hayashi

Shimizu

et al. 2006

Chemistry A European J

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The orientational effect of p-YC6H4 (Ar) on delta(Se) is elucidated for ArSeR, based on experimental and theoretical investigations. The effect is examined in the cases in which Se--CR in ArSeR is either in the Ar plane (pl) or is perpendicular to the plane (pd). 9-(Arylselanyl)anthracenes (1) and 1-(arylselanyl)anthraquionones (2) are employed to establish the effect in pl and pd, respectively. Large upfield shifts are observed for Y=NMe2, OMe, and Me, and large downfield shifts for Y=COOEt, CN, and NO2 in 1, relative to Y=H, as is expected. Large upfield shifts are brought by Y=NMe2, OMe, Me, F, Cl, and Br, and downfield shifts by Y=CN and NO2 in 2, relative to Y=H, with a negligible shift by Y=COOEt. Absolute magnetic shielding tensors of Se (sigma(Se)) are calculated for ArSeR (R=H, Me, and Ph), assuming pl and pd, based on the DFT-GIAO method. Observed characters are well explained by the total sigma(Se). Paramagnetic terms (sigmap(Se)) are governed by (sigmap(Se)xx+sigmap(Se)yy), in which the direction of np(Se) (constructed by 4pz(Se)) is set to the z axis. The main interaction in pl is the np(Se)-pi(C6H4)-pz(Y) type. The Y dependence in pl occurs through admixtures of 4pz(Se) in pi(SeC6H4Y) and pi*(SeC6H4Y), modified by the conjugation, with 4px(Se) and 4py(Se) in sigma(CSeX) and sigma*(CSeX) (X=H or C) under a magnetic field. The main interaction in pd is the sigma(CSeX)-pi(C6H4)-px(Y) type, in which Se-X is nearly on the x axis. The Y dependence in pd mainly arises from admixtures of 4pz(Se) in np(Se) with 4px(Se) and 4py(Se) in modified sigma*(CSeX), since np(Se) is filled with electrons. It is demonstrated that the effect of Y on sigmap(Se) in the pl conformation is the same regardless of whether Y is an electron-donor or electron-acceptor, whereas for pd conformations the effect is greater when Y is an electron donor, as observed in 1 and 2, respectively. Contributions of each molecular orbital and each transition on sigmap(Se) are evaluated, which enables us to recognize and visualize the effect clearly.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Orientational Effect of Aryl Groups on ⁷⁷Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Nakanishi

Hayashi

Shimizu

et al. 2006

Chemistry A European J

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“…Cyclic oligomers of the type (RSeN), (R = Me, '~r , Ph) have been spectroscopically identified (3) and the structure of (HSeN,) has been determined by ab initio calculations (4). In an attempt to make related eight-membered rings of the type (RC),N,(SeR), we found that the reaction of PhCN2(SiMe3)2 with RSeC13 (R = Me, Ph) unexpectedly produces the intensely coloured diazenes l a (A, , , = 502 nm) and l b (A, , , = 553 nm) (5).…”

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confidence: 99%

Molecular and electronic structures of the purple chromophore RC(NH₂)(NSePh) (R = H, 4-CH₃C₆H₄)

Chivers¹,

McGregor²,

Parvez³

et al. 1995

Can. J. Chem.

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The reaction of Li[4-CH3C6H4C(NSiMe3)2] with PhECl (E = S, Se) in a 1:1 molar ratio produces the monosubstituted derivatives 4-CH3C6H4C(NEPh)[N(SiMe3)2] (3b, E = Se; 3d, E = S). The thermolysis of 3b at 130 °C produces PhSeN(SiMe3)2 and 4-CH3C6H4CN. Crystals of 3b slowly acquire a purple stain upon prolonged standing at 23 °C owing to the formation of 4-CH3C6H4C(NH2)(NSePh) (4c, λmax = 551 nm). The formamidine derivative HC(NH2)(NSePh) (4a, λmax = 472 nm) was isolated from the reaction of HCN2(SiMe3)3 with PhSeCl (1:3 molar ratio) in dichloromethane. The structure of 4a was shown by X-ray crystallography to involve a syn configuration at the [Formula: see text] bond and hydrogen bonding between amino nitrogen atoms. The crystals of 4a are monoclinic, space group P21 (No. 4), with a = 7.514(1), b = 5.575(1), c = 8.925(1) Å, β = 100.71(1)°, V = 367.40(6) Å3, and Z = 2. The final R and Rw values were 0.055 and 0.060, respectively. The 1H and 77Se NMR spectra indicate that both 4a and 4c exist as a mixture of tautomers in THF solution. DFT calculations for the model tautomers HC(NH2)(NER) and HC(NH)(NHER) (E = S, Se; R = H, Ph) show that the former is more stable in all cases, but the difference in total bonding energy is smaller for selenium than for sulfur (17.5 vs. 29 kJ mol−1). The visible absorption band for 4a is assigned to the HOMO–LUMO transition (ΔE = 2.90 eV, λmax = 427 nm) of the minor tautomer. Keywords: formamidine, tautomer, selenium, purple chromophore.

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Intramolecular Se⋅⋅⋅N Nonbonding Interactions in Low-Valent Organoselenium Derivatives: A Detailed Study by1H and77Se NMR Spectroscopy and X-Ray Crystallography

Mugesh¹,

Panda²,

Singh³

et al. 1999

Chem. Eur. J.

124

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A series of novel low-valent organoselenium compounds stabilized by Se´´´N intramolecular interactions has been synthesized. The existence of Se´´´N nonbonding interactions was determined by 1 H and 77 Se NMR spectroscopy and X-ray crystallography. These interactions result in an apparent downfield shift of the 77 Se NMR signals; the shift values roughly correspond with the strength of the Se´´´N interaction. Single-crystal X-ray studies show that the strength of the Se´´´N interactions depends on the relative electronegativity of the group attached to the selenium and the nature of the heteroatom. These interactions lengthen the SeÀX (X Se, Cl, Br, I, CH 2 À ) bond trans to the N´´´Se bond and increase the possibility of nucleophilic attack on the selenium. In 77 Se chemical shift was attempted.

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Unusual attractive interactions between selenium and oxygen in selenoiminoquinones

Cited by 97 publications

References 0 publications

Orientational Effect of Aryl Groups on ⁷⁷Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Orientational Effect of Aryl Groups on ⁷⁷Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Molecular and electronic structures of the purple chromophore RC(NH₂)(NSePh) (R = H, 4-CH₃C₆H₄)

Intramolecular Se⋅⋅⋅N Nonbonding Interactions in Low-Valent Organoselenium Derivatives: A Detailed Study by1H and77Se NMR Spectroscopy and X-Ray Crystallography

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Unusual attractive interactions between selenium and oxygen in selenoiminoquinones

Cited by 97 publications

References 0 publications

Orientational Effect of Aryl Groups on 77Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Orientational Effect of Aryl Groups on 77Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Molecular and electronic structures of the purple chromophore RC(NH2)(NSePh) (R = H, 4-CH3C6H4)

Intramolecular Se⋅⋅⋅N Nonbonding Interactions in Low-Valent Organoselenium Derivatives: A Detailed Study by1H and77Se NMR Spectroscopy and X-Ray Crystallography

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Orientational Effect of Aryl Groups on ⁷⁷Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Orientational Effect of Aryl Groups on ⁷⁷Se NMR Chemical Shifts: Experimental and Theoretical Investigations

Molecular and electronic structures of the purple chromophore RC(NH₂)(NSePh) (R = H, 4-CH₃C₆H₄)