4,5-Diazafluoren-9-one

Fun, Hoong‐Kun; Sivakumar, K.; Zhu, Donghui; You, Xinkui

doi:10.1107/s0108270195003854

Cited by 11 publications

(14 citation statements)

References 3 publications

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“…Thus, the endocyclic angle at N1 is close to the trigonal value of 120˚, while that at N9 (Table 2) is equal to the average of those found at the pyridine N centres in the symmetrical parent 4,5-diazafluoren-9-one (114.95(9) and 114.09(9)˚). 5 The distances N1-C2 and C8-N9 likewise differ significantly in 1 (Table 2), the latter being identical to those reported for the parent compound (1.345(1), 1.348(2)Å). 5 The strongest interaction in the crystal is a nearly linear hydrogen bond formed between the molecule of acetic acid and the bromide ion (O31-H·Br27, with H·Br 2.43 Å, O·Br 3.263(2)Å and ∠O-H·Br 174˚).…”

supporting

confidence: 72%

“…5 The distances N1-C2 and C8-N9 likewise differ significantly in 1 (Table 2), the latter being identical to those reported for the parent compound (1.345(1), 1.348(2)Å). 5 The strongest interaction in the crystal is a nearly linear hydrogen bond formed between the molecule of acetic acid and the bromide ion (O31-H·Br27, with H·Br 2.43 Å, O·Br 3.263(2)Å and ∠O-H·Br 174˚). Additional hydrogen bonds stabilizing the crystal structure are of the type C-H·O(nitro), involving each of the atoms C6, C7 and C8 with a different symmetry-related cation and with C·O distances in the range 3.133(3) -3.399(3)Å.…”

supporting

confidence: 72%

“…An examination of the tricyclic system showed that the maximum deviation from the least-squares plane including the C and N atoms is only 0.024(2)Å (for atom C11), with atom O14 deviating by 0.063(2)Å from the former plane. This is analogous to the situation in the planar parent molecule, 4,5-diazafluoren-9-one, 5 and in sharp contrast to the situation recently found in a compound containing the pyrrolodiazafluoren-5-one system, 2 where the more congested tetracyclic ring system is significantly distorted due to an abnormally short intramolecular N·C contact of 2.797(2)Å. In the case of 1, the absence of a fourth (pyrrolo) ring relieves the steric strain and the closest intramolecular contact in 1, C15·N9, is significantly longer, namely 2.936(3)Å.…”

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confidence: 68%

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X-ray Structure of N-(4-Nitrophenacyl)-4,5-diazafluoren-9-onium Bromide

et al. 2007

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Helicity may be induced via intramolecular strain. This type of distortion has usually been associated with systems containing five or more ortho-condensed aromatic rings.1 Recently, helical distortion was detected by NMR spectroscopy and X-ray analysis in novel tetracyclic moieties synthesized from 1,10-phenanthrolinium and 4,5-diazafluorenonium salts.2 Also, in the NMR spectra of N-phenacyl 1,10-phenanthrolinium bromides, the methylenic protons appear as a broad singlet, suggesting a strained stereostructure due to an intramolecular hydrogen bond near the coalescence temperature, which was eventually proved by X-ray analysis.3 However, in the case of 4,5-diazafluorenonium salts, the methylenic signal appears as a sharp singlet, indicating no intramolecular strain, or less strain than in the case of N-(4-chlorophenacyl)phenanthrolinium bromides.3 Furthermore, preliminary molecular modeling with various methods, such as MM2, MM3, PM5 and MNDOd, resulted in a planar structure for the 4,5-diazafluorenonium moiety. In order to verify these deductions, the representative compound 1 (Fig. 1) was subjected to X-ray analysis. Compound 1 was prepared according to a reported method 4 from 4,5-diazafluoren-9-one and 2-bromo-4′-nitroacetophenone. Suitable crystals for X-ray crystallography were obtained by recrystallization from acetic acid.A single crystal measuring 0.15×0.08×0.15 mm was selected for intensity data collection, mounted on a diffractometer and cooled in a continuous stream of nitrogen vapor at 113±2 K. Structure solution by direct methods revealed that a molecule of acetic acid co-crystallizes with the formula unit 1, yielding a solvate. All hydrogen atoms were first located in difference Fourier maps and subsequently added at idealized positions with Uiso set at 1.2-times those of their parent atoms. A full-matrix The quaternization of a nitrogen atom of the 4,5-diazafluoren-9-one molecule, manifested in the title cation, introduces significant asymmetry, reflected in differences in the geometries of the two pyridyl moieties. In constrast to related, previously reported tetracyclic systems that display a high degree of helical distortion, steric congestion in the title cation is minimal, rendering the 4,5-diazafluoren-9-onium moiety virtually planar. This is consistent with predictions based on NMR spectroscopy.

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confidence: 72%

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confidence: 72%

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confidence: 68%

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X-ray Structure of N-(4-Nitrophenacyl)-4,5-diazafluoren-9-onium Bromide

et al. 2007

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“…For these two N atoms, the charge concentration is greater on one (N1 in this case) than the other, which is justified by the shorter donoracceptor distance O1W...N1. This is also observed in the structure of 4,5-diazafluoren-9-one, where only one N atom is involved in a C--H...N hydrogen bond (Fun, Sivakumar, Zhu & You, 1995).…”

Section: Commentmentioning

confidence: 64%

p-Dimethylaminobenzaldehyde 4,5-Diaza-9-fluorenylidenehydrazone Monohydrate

Lu¹,

Duan²,

Tian³

et al. 1995

Acta Crystallogr C

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“…The two other major hydrogen bonds, N4--H4N...O1W and C15--H15..-O1, form the interlayer connections. We have observed previously that due to the possibility of different charge concentrations between the two pyridinyl N atoms of the diazafluorene moiety, the one with the greater charge is involved in the stronger intermolecular hydrogen bonds, whereas the other may be involved in only a weak interaction (Fun, Sivakumar, Zhu & You, 1995;Lu et al, 1995). In the title structure, the same pattern is observed; the N2 atom is involved in a strong O---H...N (O1W...N2) contact, while the N1 atom has a very weak interaction with the C17 atom in the form of a C--H...N contact.…”

mentioning

confidence: 99%