15072-08-9Relevant articles and documents
Molecular recognition: Preorganization of a bis(pyrrole) schiff base derivative for tight dimerization by hydrogen bonding
Munro, Orde Q.,Joubert, Sandra D.,Grimmer, Craig D.
, p. 7987 - 7999 (2006)
Multiple techniques have been used to delineate the self-assembly of a bis(pyrrole) Schiff base derivative (compound 4, C16H 14N4), which forms an unusual dimer through complementary N-H...N=C hydrogen bonds between twisted, C2-symmetric monomer units. The asymmetric unit of the crystal structure comprises one and a half dimer units, with one dimer exhibiting approximate D2 point-group symmetry and the other exact D2 symmetry (space group C2/c). The dimers pack into columns whose axes are collinear with the a axis of the unit cell. The columns assemble into discrete layers with two distinct types of hydrogen-sized voids residing between the layers. Despite the promising architec ture of the voids within the lattice of 4, the absence of genuine channels to interconnect the voids precludes the uptake of hydrogen gas, even at elevated pressures (10 bar). AM1 calculations of the structure of dimeric 4 indicate that self-recognition through hydrogen bonding depends primarily on favorable electrostatic interactions. The potential-energy surface for monomeric 4 mapped by counter-rotation of an adjacent pair of C=C-N=C torsion angles indicates that the X-ray structures of the four monomeric units are global minima with highly nonplanar conformations that are preorganized for self-recognition by hydrogen bonding. The in vacuo enthalpy of association for the dimer was calculated to be significantly exergonic (ΔGassoc = -21.9 kJ mol-1, 298 K) and in excellent agreement with that determined by 1H NMR spectroscopy in CDCl3 (AGassoc = -16.6(4) kJ mol -1, 298 K). Using population and bond order analyses, in conjunction with the conformation dependence of the frontier MO energies, we have been able to show that π-electron delocalization is only marginally diminished in the nonplanar conformers of 4 and that the electronic structures of the constituent monomers of the dimer are well mixed.
Luminescent di- and trinuclear boron complexes based on aromatic iminopyrrolyl spacer ligands: Synthesis, characterization, and application in OLEDs
Suresh,Gomes, Clara S. B.,Lopes, Patrícia S.,Figueira, Cláudia A.,Ferreira, Bruno,Gomes, Pedro T.,Di Paolo, Roberto E.,Ma?Anita, Ant?nio L.,Duarte, M. Teresa,Charas, Ana,Morgado, Jorge,Vila-Vi?osa, Diogo,Calhorda, Maria José
, p. 9133 - 9149 (2015/06/16)
New bis- and tris(iminopyrrole)-functionalized linear (1,2-(HNC4H3-C(H)-N)2-C6H4 (2), 1,3-(HNC4H3-C(H)-N)2-C6H4 (3), 1,4-(HNC4H3-C(H)-N)2-C6H4 (4), 4,4′-(HNC4H3-C(H)-N)2-(C6H4-C6H4) (5), 1,5-(HNC4H3C-(H)-N)2-C10H6 (6), 2,6-(HNC4H3C-(H)-N)2-C10H6 (7), 2,6-(HNC4H3C-(H)-N)2-C14H8 (8)) and star-shaped (1,3,5-(HNC4H3-C(H)-N-1,4-C6H4)3-C6H3 (9)) π-conjugated molecules were synthesized by the condensation reactions of 2-formylpyrrole (1) with several aromatic di- and triamines. The corresponding linear diboron chelate complexes (Ph2B[1,3-bis(iminopyrrolyl)-phenyl]BPh2 (10), Ph2B[1,4-bis(iminopyrrolyl)-phenyl]BPh2 (11), Ph2B[4,4′-bis(iminopyrrolyl)-biphenyl]BPh2 (12), Ph2B[1,5-bis(iminopyrrolyl)-naphthyl]BPh2 (13), Ph2B[2,6-bis(iminopyrrolyl)-naphthyl]BPh2 (14), Ph2B[2,6-bis(iminopyrrolyl)-anthracenyl]BPh2 (15)) and the star-shaped triboron complex ([4′,4′′,4′′′-tris(iminopyrrolyl)-1,3,5-triphenylbenzene](BPh2)3 (16)) were obtained in moderate to good yields, by the treatment of 3-9 with B(C6H5)3. The ligand precursors are non-emissive, whereas most of their boron complexes are highly fluorescent; their emission color depends on the π-conjugation length. The photophysical properties of the luminescent polyboron compounds were measured, showing good solution fluorescence quantum yields ranging from 0.15 to 0.69. DFT and time-dependent DFT calculations confirmed that molecules 10 and 16 are blue emitters, because only one of the iminopyrrolyl groups becomes planar in the singlet excited state, whereas the second (and third) keeps the same geometry. Compound 13, in which planarity is not achieved in any of the groups, is poorly emissive. In the other examples (11, 12, 14, and 15), the LUMO is stabilized, narrowing the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO), and the two iminopyrrolyl groups become planar, extending the size of the π-system, to afford green to yellow emissions. Organic light-emitting diodes (OLEDs) were fabricated by using the new polyboron complexes and their luminance was found to be in the order of 2400 cd m-2, for single layer devices, increasing to 4400 cd m-2 when a hole-transporting layer is used. Bridge the gap: Luminescent linear and star-shaped polynuclear organoboron complexes containing iminopyrrolyl ligands linked by aryl bridges were synthesized, showing good luminescent properties depending on π-conjugation lengths of the molecules (see figure). Organic light-emitting diodes (OLEDs) were successfully fabricated with the new boron complexes, achieving luminance values of up to 4400 cd m-2.
Synthesis, properties, and reactivity of a series of non-heme {FeNO} 7/8 complexes: Implications for Fe-nitroxyl coordination
Sanders, Brian C.,Patra, Ashis K.,Harrop, Todd C.
, p. 115 - 127 (2013/02/23)
The biochemical properties of nitroxyl (HNO/NO-) are distinct from nitric oxide (NO). Metal centers, particularly Fe, appear as suitable sites of HNO activity, both for generation and targeting. Furthermore, reduced Fe-NO-/Fe-HNO or
