62938-08-3Relevant articles and documents
Platinum and palladium complexes of tridentate ?C^N^N (phen-ide)-pyridine-thiazol ligands – A case study involving spectroelectrochemistry, photoluminescence spectroscopy and TD-DFT calculations
Krause, Maren,von der Stück, René,Brünink, Dana,Buss, Stefan,Doltsinis, Nikos L.,Strassert, Cristian A.,Klein, Axel
supporting information, (2021/01/25)
Four Pd(II) and Pt(II) complexes [M(C^N^N)Cl] (HC^N^N = 2-(6-phenylpyridin-2-yl)thiazoles) were synthesised, analysed and characterised using 1H NMR and MS in solution, as well as single crystal XRD in the solid. Cyclic voltammetry of the square planar complexes showed reversible or partially reversible reductions and irreversible oxidations. DFT calculations allowed assigning them to essentially metal-centred oxidations and ligand-centred reductions. Absorption spectra of the complexes show intense absorption bands into π-π* states in the UV to visible spectral range and long-wavelength bands which were assigned to transitions into mixed metal-to-ligand charge transfer (MLCT)/π-π* states, based on TD-DFT calculations. Comparison of Pt and Pd derivatives showed that the energy of the (MLCT)/π-π* bands are increased for Pd over Pt. This was also observed for the phosphorescence at 77 K and is attributed to the higher oxidation potential for Pd and supported by spectroelectrochemical measurements. The photoluminescence quantum yield (ΦL) drops drastically from Pt to Pd at room temperature, where only the two Pt(II) complexes are luminescent showing a broad unstructured phosphorescence from a 3MLCT state. At 77 K, the phosphorescence is blue-shifted and shows a clear vibrational progression, which is related to an enhanced ligand-centred character due to the lack of solvent stabilisation in the frozen matrix that otherwise increases the MLCT contribution. The Pd(II) complexes are not emissive at 298 K, but luminesce at 77 K. This is due to metal-centred dissociative d-d* states that facilitate radiationless deactivation, which cannot be thermally populated at low temperatures. Thus, similar ΦL are observed in frozen glassy matrices for both metals. TD-DFT calculations provided insight into the excited states and showed that the substitution pattern does not affect the emission, due to the lack of participation of the phenyl unit in the orbitals that are relevant for the description of the emissive state.
An efficient synthesis of porphyrins with different meso substituents that avoids scrambling in aqueous media
Nowak-Krl, Agnieszka,Plamont, Rmi,Canard, Gabriel,Edzang, Judicaelle Andeme,Gryko, Daniel T.,Balaban, Teodorsilviu
supporting information, p. 1488 - 1498 (2015/01/30)
We have developed new conditions that afford regioisomerically pure trans-A2B2-, A3B-, and trans-AB2C-porphyrins bearing aryl and arylethynyl substituents. The porphyrins were prepared by the acid-catalyzed condensation of dipyrromethanes with aldehydes followed by oxidation with p-chloranil or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Optimal conditions for the condensation were identified after examining various reaction parameters such as solvent composition, acid concentration, and reaction time. The conditions identified (for aromatic aldehydes: EtOH/H2O 4:1, [DPM] = 4 mM, [aldehyde] = 4 mM, [HCl] = 38 mM, 16 h; for arylethynyl aldehydes: THF/H2O 2:1, [DPM] = 13 mM, [aldehyde] = 13 mM, [HCl] = 150 mM, 3 h) resulted in the formation of porphyrins in yields of 9-38% without detectable scrambling. This synthesis is compatible with diverse functionalities such as ester or nitrile. In total, 20 new trans-A2B2-, A3B-, and trans-AB2C-porphyrins were prepared. The scope and limitations of the two sets of reaction conditions have been explored. The methodological advantage of this approach is its straightforward access to building blocks and the formation of the porphyrin core in higher yields than by any other methodology and by using environmentally benign and nonhazardous chemicals.
Synthesis of trans-A2B2- and trans-A2BC-porphyrins with polar 4′-(dimethylamino)tolan-4-yl substituents, and a screening protocol for vapor-phase deposition on metal surfaces
Alberti, Mariza N.,Nowakowska, Sylwia,Tzirakis, Manolis D.,Nowakowski, Jan,Fesser, Petra,Schweizer, W. Bernd,Shchyrba, Aneliia,Thilgen, Carlo,Jung, Thomas A.,Diederich, Fran?ois
supporting information, p. 5705 - 5719 (2014/10/16)
The role of polar 4-[p-(dimethylamino)phenylethynyl]phenyl substituents, with a calculated dipole moment of 3.35 Debye, in the self-assembly of trans-A2B2- and A2BC-substituted porphyrins was explored in the solid state by X-ray crystallography, and on an Au(111) surface by scanning tunneling microscopy (STM). Our results demonstrate that the dipolar character of these substituents blocks the 2D self-assembly of porphyrins into larger ordered domains on Au(111) at low coverage, whereas antiparallel dipole - dipole interactions govern the molecular ordering in the crystal. The STM analysis revealed an adaptation of the conformation of the prochiral building blocks and a site-selectivity of the adsorption. We present a general protocol for testing the suitability of higher-molecular-weight compounds, such as porphyrins, to be deposited on surface by sublimation in ultra-high vacuum (UHV). This protocol combines classical methods of chemical analysis with typical surface science techniques.
