Methoxyxanthobilirubinic acid methyl ester (methyl 3-{5-[(3-ethyl-5-methoxy-4-methyl-2H-pyrrol-2-ylidene)methyl]-2,4-dimethyl-3-pyrrolyl}propanoate), C19H26N2O3

Dattagupta, J.K.; Meyer, Erik; Cullen, David L.; Falk, H.; Gergely, S.

doi:10.1107/s0108270183008604

Cited by 5 publications

(5 citation statements)

References 4 publications

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“…The experimentally determined nitrogennitrogen distance and methine bridge angle of methoxyxanthobilirubinic acid methyl ester are 2.718 Å and 127°, respectively. 34 These values compare well with those calculated for monomeric HMPM, i.e., 2.777 Å and 126.6°, respectively. Further details of the structural differences between HMPM monomer and dimer will be discussed in a subsequent paper.…”

Section: Resultssupporting

confidence: 82%

“…This conclusion is supported by the good agreement between the calculated structure of the HMPM monomer with the crystal structure of a related pyrromethene, i.e., methoxyxanthobilirubinic acid methyl ester, which exhibits a similar intramolecular hydrogen bond. The experimentally determined nitrogen−nitrogen distance and methine bridge angle of methoxyxanthobilirubinic acid methyl ester are 2.718 Å and 127°, respectively . These values compare well with those calculated for monomeric HMPM, i.e., 2.777 Å and 126.6°, respectively.…”

Section: Resultssupporting

confidence: 80%

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Calculation of the Vibrational Spectra of Linear Tetrapyrroles. 2. Resonance Raman Spectra of Hexamethylpyrromethene Monomers

et al. 2000

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The resonance Raman (RR) spectra of monomeric 3,3‘,4,4‘,5,5‘-hexamethylpyrromethene (HMPM) were measured upon excitation in resonance with the strong 436 nm absorption band. The experimental spectra were analyzed by comparison with calculated RR spectra that were obtained on the basis of scaled quantum chemical force fields in combination with the transform theory. The ground-state structure and force field of HMPM were calculated by density functional theory (DFT) using the B3LYP exchange functional and the 6-31G* basis set. The monomeric HMPM adopts a planar structure in contrast to HMPM dimers in which the intermolecular hydrogen-bonding interactions induce a slight torsion of the methine bridges as revealed by both the experimental and the calculated structures. The force fields were scaled by using a global set of scaling factors determined previously (Magdó, I.; Németh, K.; Mark, F.; Hildebrandt, P.; Schaffner, K. J. Phys. Chem. A 1999, 103, 289). To account for the effect of the intramolecular hydrogen bond between the pyrrolic N−H group and the pyrroleninic nitrogen in the monomeric HMPM, only the scaling factor for the N−H in-plane bending force constant required a slight adjustment. Electronic transitions were calculated by means of CNDO/S, Hartree−Fock single configuration interaction (HF-CIS), and time-dependent DFT, which all predict one strong and one or two adjacent weak transitions for the lowest electronic excitations. This pattern is in line with band fitting analyses of the 436 nm absorption band. The best agreement in excitation energies was obtained by time-dependent DFT calculations. Excited-state displacements as required for evaluating RR intensities were determined for the lowest excited singlet state S1 using the equilibrium geometries optimized for the ground and excited states by means of the HF and HF-CIS methods, respectively. For the second lowest excited state (S2), only an approximate equilibrium geometry could be used for determining the excited-state displacements as the S2 state became quasi-isoenergetic with the S1 state during the geometry optimization. Employing the transform theory, RR spectra were calculated for resonance enhancement via the S1 and S2 states. The experimental RR spectrum of HMPM excited at 413 nm agrees well with the calculated S1-RR spectrum, allowing a plausible and consistent vibrational assignment for most of the observed bands of HMPM and its isotopomer deuterated at the pyrrolic nitrogen. The root-mean-square deviations between the experimental and calculated frequencies are 7 and 5 cm-1 for nondeuterated and deuterated HMPM, respectively. Experimental RR intensities and their dependence on the excitation wavelength are reproduced in a semiquantitative manner. The only significant exceptions refer to the CC stretching and CH rocking modes of the methine bridge, ν21 and ν49. On one hand, these discrepancies may reflect intrinsic deficiencies of the HF/HF-CIS method in calculating excited-state displacements. On the other hand, the unique deviation o...

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Section: Resultssupporting

confidence: 82%

Section: Resultssupporting

confidence: 80%

Calculation of the Vibrational Spectra of Linear Tetrapyrroles. 2. Resonance Raman Spectra of Hexamethylpyrromethene Monomers

et al. 2000

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“…Interestingly, the 148.78 C4-C5-C6 angle in the free-base 1 is much larger than in the known free-bases 7 28 34 (within the range 132.18-136.08), despite the fact that all bear hydrogen atoms at the meso position. The significantly different sizes in the C4-C5-C6 angle are presumably a consequence of (i) the substituents that Fig.…”

Section: Resultsmentioning

confidence: 80%

The first series of alkali dipyrrinato complexes

et al. 2010

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The first series of alkali dipyrrinato complexes is reported, encompassing lithium, sodium, and potassium salts of meso-unsubstituted and meso-aryl-substituted derivatives. By varying the substituents at the meso position, the intermolecular distance between the two nitrogen atoms and thus the k 2 -N,N-bidentate bite angle was altered, as confirmed by comparison of crystallographic structures of dipyrrin free-bases in the solid-state. The mode of bonding varies as the ionic radius of the metal ion increases: solid-state structures reveal lithium to be accommodated in the plane of the dipyrrinato unit, whilst sodium is accommodated out of plane. The reactivity of analogous lithium, sodium, and potassium dipyrrinato complexes increases as the ionic radius of the metal ion increases, in keeping with the concept that the complexes tend towards an increasingly ionic nature as the size of the alkali metal increases.Résumé : On rapporte la préparation de la première série de complexes dipyrrinato alcalins comportant les sels de lithium, de sodium et de potassium de dérivés méso non substitués et méso substitués par des groupes aryles. En faisant varier la nature des substituants en position méso, on modifie la distance intermoléculaire entre les deux atomes d'azote et, en conséquence, l'angle de morsure k 2 -N,N du bidentate, tel que confirmé par une comparaison des structures cristallographiques des bases libres dipyrrines à l'état solide. Le mode de liaison varie avec une augmentation du rayon ionique de l'ion métallique; les structures à l'état solide révèlent que le lithium s'accommode dans le plan de l'unité dipyrrinato alors que le sodium est accommodé hors du plan. La réactivité des complexes analogues du lithium, du sodium et du potassium augmente avec une augmentation du rayon ionique du métal ionique, en accord avec le concept que les complexes tendent vers une nature de plus en plus ionique avec une augmentation de la taille des métaux alcalins.

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“…In these molecules the intramolecular N···N distances are found to be ca. 0.15 Å shorter than in HMPM crystals. , Also the two additional intermolecular hydrogen bonds that are formed within the dimeric entity are weaker compared to hydrogen bonds between secondary amines and sp 2 hybridized nitrogen atoms as these systems display distinctly shorter N···N distances (2.96 ± 0.13 Å) . Thus, formation of HMPM dimers is determined by the tradeoff of two opposing effects, i.e., the energy gain due to formation of additional albeit relatively weak intermolecular hydrogen bonds and the energy loss due to weakening of the intramolecular hydrogen bonds.…”

Section: Resultsmentioning

confidence: 93%

Calculation of Vibrational Spectra of Linear Tetrapyrroles. 3. Hydrogen-Bonded Hexamethylpyrromethene Dimers

et al. 2005

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The structure and vibrational spectra of hexamethylpyrromethene (HMPM) have been investigated by X-ray crystallography, IR and Raman spectroscopies, and density functional theory calculations. HMPM crystallizes in the form of dimers, which are held together by bifurcated N-H(...N)(2) hydrogen bonds, involving one intramolecular and one intermolecular N-H...N interaction. The monomers are essentially planar, and the mean planes of the monomers lie approximately perpendicular to one another, so that the four N atoms in the dimer form a distorted tetrahedron. The structure of the HMPM dimer is well-reproduced by B3LYP/6-31G calculations. A comparison of the calculated geometry of the dimer with that of the monomer reveals only small changes in the N-H...N entity and the methine bridge angles upon dimerization. These are a result of weakening of the intramolecular N-H...N hydrogen bond and the formation of a more linear N-H...N intermolecular hydrogen bond. Using an empirical relation between the shift of the N-H stretching frequency of pyrrole and the enthalpy of adduct formation with bases [Nozari, M. S.; Drago, R. S. J. Am. Chem. Soc. 1970, 92, 7086-7090], estimates of the strength of the intra- and intermolecular hydrogen bonds are obtained. IR and Raman spectroscopies of HMPM and its isotopomers deuterated at the pyrrolic nitrogen atom and at the methine bridge reveal that the molecule is monomeric in nonpolar organic solvents but dimeric in a solid Ar matrix and in KBr pellets. The matrix IR spectra show a splitting of vibrational modes for the dimer, particularly those involving the N-H coordinates. Due to intrinsic deficiencies of the B3LYP/6-31G approximation, a satisfactory reproduction of these modes of the monomeric and dimeric HMPM requires specific adjustments of the NH scaling factors for the calculated force constants and, in the case of the NH out-of-plane modes of HMPM dimers, also of intra- and intermolecular coupling constants. This parametrization does not significantly affect the other calculated modes, which in general reveal a very good agreement with the experimental data.

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Methoxyxanthobilirubinic acid methyl ester (methyl 3-{5-[(3-ethyl-5-methoxy-4-methyl-2H-pyrrol-2-ylidene)methyl]-2,4-dimethyl-3-pyrrolyl}propanoate), C19H26N2O3

Cited by 5 publications

References 4 publications

Calculation of the Vibrational Spectra of Linear Tetrapyrroles. 2. Resonance Raman Spectra of Hexamethylpyrromethene Monomers

Calculation of the Vibrational Spectra of Linear Tetrapyrroles. 2. Resonance Raman Spectra of Hexamethylpyrromethene Monomers

The first series of alkali dipyrrinato complexes

Calculation of Vibrational Spectra of Linear Tetrapyrroles. 3. Hydrogen-Bonded Hexamethylpyrromethene Dimers

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