Raman Studies of Bis(phenylterpyrazine)iron(ii) and Supramolecular Species With Pentacyanidoferrate(ii) Ions

Abstract

The chemistry and spectroscopy of the iron(II) phenylterpyrazine complex, [Fe(phtpz) 2 ] 2+ , were investigated in comparison with the analogous phenylterpyridine species, Fe(phtpy) 2 ] 2+ , and the results indicated a strong electronic delocalization on the Fe(II) terimine chromophore encompassing the lateral pyrazyl groups. The delocalized nature of the molecular orbitals involved in the electronic excitation precluded a direct assignment of the pyridine and pyrazine vibrations in the complex. However, the capability of the terpyrazine complex to bind transition metal ions, such as the [Fe(CN) 5 ] 3species, allowed to generate pentanuclear complexes displaying characteristic charge-transfer and resonance Raman spectra, revealing the pyrazine vibrations in the complex. The [Fe(CN) 5 ] 3containing species also yielded polymeric compounds in presence of transition metal ions, exhibiting intervalence transfer bands and chemical similarities with the Prussian Blue complex.

Strategic Modulation of Target-Specific Isolated Fe,Co Single-Atom Active Sites for Oxygen Electrocatalysis Impacting High Power Zn–Air Battery

“…This is unlike the pyrolyzed sample Fe,Co,N−C, where significant D and G bands could be observed with I D /I G = 1.02 due to the metal/N codoped carbon framework and the C−CC sp 2 hybridized C moiety, respectively, of which the latter resembled planarity. 43,44 As expected, no observable peaks in the 100− 600 cm −1 range indicates that there was no metal (hydro)oxide formation either in Fe,Co,btpy or in Fe,Co,N−C samples.…”

“…Besides this, the Raman spectra in Figure g suggested that, in the Fe,Co,btpy sample, an obvious metal–ligand framework showed a Soret band corresponding to the M–N vibration was at 656.9 cm –1 , and few out of plane vibrations for C–C, C–N, C–H, and CC could be evidenced at around 1038.7, 1284.8, 1359.3, 1469.3, and 1605.4 cm –1 , respectively. This is unlike the pyrolyzed sample Fe,Co,N–C, where significant D and G bands could be observed with I D / I G = 1.02 due to the metal/N codoped carbon framework and the C–CC sp 2 hybridized C moiety, respectively, of which the latter resembled planarity. , As expected, no observable peaks in the 100–600 cm –1 range indicates that there was no metal (hydro)­oxide formation either in Fe,Co,btpy or in Fe,Co,N–C samples.…”

Impact of the outer‐sphere and inner‐sphere association in the surface enhanced Raman spectra of metal complexes and gold nanoparticles

“…The compound 4 0 -phenyl-2,2 0 :6,2 0 -terpyridine (pytpy) was prepared and characterized previously. 17 The 4 0 -pyridyl-2,2 0 :6,2 0 -terpyrazine (pytpz) was obtained by adapting a previously reported procedure 18 : 2.5 g of 2-acetylpyrazine (20 mmol) was mixed with 1 mL of 4-pyridylcarboxyaldehyde (10 mmol) and 30 mL of ethanol. After complete dissolution, 1.58 g of KOH and 24 mL of NH 4 OH (18 mol L À1 ) were added, and the mixture was kept under magnetic stirring, at room temperature, for 6 h. The solid product was collected on a filter and washed with water until it obtained a neutral pH.…”

“…The product was recrystallized from a chloroform/ethanol mixture ( The [Fe (phtpy) 2 ](PF 6 ) 2 complex was prepared and characterized previously. 17 The [Fe (pytpz) 2 ](PF 6 ) 2 complex was prepared by adapting the previously reported procedure for the [Fe (phtpy) 2 ](PF 6 ) 2 analog. 17 In a typical procedure, (NH 4 ) 2 Fe(SO 4 ) 2 Á6H 2 O, 200 mg, was dissolved in 35 mL of water, under a nitrogen atmosphere and magnetic stirring.…”

Resonance Raman Excitation Profiles of Fe(II)–Terpyridine Complexes: Electronic Effects of Ligand Modifications

“…In particular, these chromophores serve as precursors for sensitizers or photocatalysts, such as metallo-supramolecular polymers (MSPs), in solar cells and other optoelectrical devices. − Suitable ligands for MSPs are commonly prepared by combining the chelating effect of tpy end units with oligothiophenes or other linkers introduced as substituents in the 4′-tpy position and by their complexation with ion couplers (transition-metal ions). − The first applications of these transition-metal complexes involved precious metals, primarily ruthenium. However, in the last 15 years, not only ruthenium but also less expensive metals such as iron have been used as photosensitizers and MSP precursors. − Both Ru­(II) and Fe­(II) polypyridine complexes exhibit a strong absorption band caused by their metal-to-ligand charge transfer (MLCT) transitions.…”