The crystal and molecular structures of two new phosphorochromones determined by single-crystal X-ray
diffraction are presented. The existence of two tautomers stabilized by intramolecular N−H···O and O−H···N
hydrogen bonds and environmental effects in crystals is observed as evidence of the proton transfer reaction.
The proton transfer process within simple enaminones being analogues of the compounds studied by X-ray
diffraction methods is investigated usingMP2/6-311++G** and MP4/6-311++G** levels of theory. The
Bader theory is also applied in the analysis of the hydrogen bonding within investigated systems. The results
indicate that the systems with N−H···O intramolecular hydrogen bonds are more stable than those containing
O−H···N bonds.
Six compounds containing N-methylpyrazoline ring fused with flavanone derivatives have been synthesized and characterized by X-ray structural studies and fluorescence spectroscopy. The influence of molecular arrangement on the emission properties, including fluorescence lifetime and quantum yield, was discussed on the basis of structural data and detailed analysis of the Hirshfeld surfaces. The correlation of fluorescence and crystal packing reveals that 1 solid state emission of this class of compounds strongly depends on intermolecular interactions present in different crystal lattice. It was observed that the inverse of fluorescence lifetime (1/τavg)is linearly dependent on a percentage contribution of H…O and H…N contacts in the Hirshfeld surface. In addition, the lipophilicity (log P) of these compounds is related to contribution of C…H interactions as well as non-covalent bonding involving a halogen atom.
Intramolecular N-H...O hydrogen bonds in 3-(aminomethylene)pyran-2,4-dione and its simple derivatives (F, Li, and BeH substituents) were analyzed theoretically. The systems were optimized at the B3LYP/6-311++G(d,p) level of approximation. For some fluorine derivatives the corresponding tautomers with O-H...N intramolecular H-bonds were investigated, and for such pairs of tautomers, the calculations on transition states of the N-H...O <--> N...H-O proton-transfer reaction were carried out. The geometrical and energetic parameters for these species were characterized. The topological parameters derived from Bader theory were also analyzed; these are characteristics of H-bond critical points and also of ring critical points. Besides N-H...O and O-H...N intramolecular hydrogen bonds, there are the other intramolecular interactions, mostly ionic such as Be(+delta)...(-delta)O, Li(+delta)...(-delta)O, and Li(+delta)...(-delta)F. The F...O interactions also exist for some of species investigated. They may be classified as energetically stabilizing ones since the corresponding bond paths and critical points exist. The numerous correlations and dependencies between geometrical, topological, and energetic parameters were detected and described.
In the current work,
comprehensive photophysical and electrochemical
studies were performed for eight rhenium(I) complexes incorporating
2,2′:6′,2″-terpyridine (terpy) and 2,6-bis(pyrazin-2-yl)pyridine
(dppy) with appended 1-naphthyl-, 2-naphthyl-, 9-phenanthrenyl, and
1-pyrenyl groups. Naphthyl and phenanthrenyl substituents marginally
affected the energy of the MLCT absorption and emission bands, signaling
a weak electronic coupling of the appended aryl group with the Re(I)
center. The triplet MLCT state in these complexes is so low lying
relative to the triplet
3
IL
aryl
that the thermal
population of the triplet excited state delocalized on the organic
chromophore is ineffective. The attachment of the electron-rich pyrenyl
group resulted in a noticeable red shift and a significant increase
in molar absorption coefficients of the lowest energy absorption of
the resulting Re(I) complexes due to the contribution of intraligand
charge-transfer (ILCT) transitions occurring from the pyrenyl substituent
to the terpy/dppy core. At 77 K, the excited states of [ReCl(CO)
3
(L
n
-κ
2
N
)] with 1-pyrenyl-functionalized ligands were found to
have predominant
3
IL
pyrene
/
3
ILCT
pyrene→terpy
character. The
3
IL/
3
ILCT nature of the lowest energy excited state of [ReCl(CO)
3
(4′-(1-pyrenyl)-terpy-κ
2
N
)] was also evidenced by nanosecond transient absorption and time-resolved
emission spectroscopy. Enhanced room-temperature emission lifetimes
of the complexes [ReCl(CO)
3
(L
n
-κ
2
N
)] with 1-pyrenyl-substituted
ligands are indicative of the thermal activation between
3
MLCT and
3
IL/
3
ILCT excited states. Deactivation
pathways occurring upon light excitation in [ReCl(CO)
3
(4′-(1-naphthyl)-terpy-κ
2
N
)] and [ReCl(CO)
3
(4′-(1-pyrenyl)-terpy-κ
2
N
)] were determined by femtosecond transient
absorption studies.
We report the influence of the substituent at the N atom of the ligands on the synthesis, biological activity, and stability of Pd(II) complexes of the general formula PdL(2). The compounds adopt a cis or trans configuration with respect to the substituent at the nitrogen atom. Sterically hindered substituents promote the formation of trans isomers, whereas when the nitrogen atom is unsubstituted, cis isomers are formed. The compounds were characterized by elemental analysis, infrared and 1H NMR spectroscopies, and electrospray mass spectrometry. The complexes were also studied using X-ray diffraction and computational DFT methods. Both complexes cis-3a and trans-3c exhibit square-planar geometries around the Pd(II) atom. The cytotoxic effects of these complexes were examined on two human leukemia cell lines, HL-60 and NALM-6. Pd complex cis-3a showed significant cytotoxic activity. The effects exhibited by this complex were comparable to those reported for carboplatin. Loigand 2a was not cytotoxic. Computational analysis carried out at the PB/B3LYP/LACVP**//mPW1PW91/LanL2DZ level showed excellent correlation between the energy difference of the cis and trans isomers and the cytotoxic activity, rendering computations a useful predictive tool for the design of new drugs.
The intramolecular N-HÁÁÁO hydrogen bonds in 3-aminomethylene-2 methoxy-5,6-dimethyl-2-oxo-2, 3-dihydro-2k 5 -[1,2]oxaphosphinin-4-one and its derivatives (F, H, Li, -BeH) were studied by DFT (density functional theory) methods. The results of calculations were obtained at B3LYP/6-311??G(d,p) level on model species, with the resonance-assisted hydrogen bonds (RAHB). Topological parameters such an electron density, its Laplacian, kinetic electron energy density, potential electron energy density, and total electron energy density at the bond critical points (BCP) of HÁÁÁO/N-H contact bonds from Bader's 'Atoms in molecules' (AIM) theory were analyzed in details. The energy of the N-HÁÁÁO interactions studied here was found rather weak (E HB = 2.53-12.08 kcal/mol). The results of AIM ellipticity indicated p-delocalization over all six atoms within ring.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.