Synthesis, Structure, Spectroscopic Properties, and Electrochemistry of Rare Earth Sandwich Compounds with Mixed 2,3-Naphthalocyaninato and Octaethylporphyrinato Ligands

Abstract

A series of 14 heteroleptic rare earth sandwich complexes [M(III)-(nc)(oep)] (M=Y, La-Lu except Ce and Pm; nc=2,3-naphthalocyaninate; oep = octaethylporphyrinate) have been prepared by a one-pot procedure from corresponding [M(acac)3] . nH2O (acac = acetylacetonate), metal-free porphyrin H2(oep), and naphthalonitrile the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) in n-octanol. The molecular structures of four of these complexes (M = Sm, Gd, Y, Lu) are isostructural, exhibiting a slightly distorted square antiprismatic geometry with two domed ligands. The interplanar distance decreases from 2.823 to 2.646 A along the series as a result of lanthanide contraction. The whole series of complexes have also been characterized spectroscopically. All the electronic absorptions, except the two B-bands due to nc and the oep rings, are metal-dependent, indicating that there are substantial pi-pi interactions. The hole or the unpaired electron in these double-deckers is delocalized over both macrocyclic ligands, as evidenced by the co-appearance of the IR marker bands for the nc*- (1315-1325 cm(-1)) and oep*- (1510-1531 cm(-1)) T radical ions. Three one-electron oxidation couples and up to three one-electron reduction couples have been revealed by electrochemical methods. All the potentials are linearly dependent on the size of the metal center. The changes in absorption spectra during the first electro-oxidation and reduction of the La(III), Eu(III), and Y(III) double-deckers have also been studied spectroelectrochemically. The spectral data recorded for [M(III)(nc)(oep)]-(M = Y, La-Lu except Ce and Pm) reduced chemically with hydrazine hydrate are in accord with those obtained by spectroelectrochemical methods. The first heteroleptic naphthalocyaninate-containing triple-deckers [M(III)2(nc)-(oep)2] (M = Nd, Eu) have also been prepared by a raise-by-one-story method by using [M(III)(nc)(oep)] (M = Nd, Eu), [M(acac)3] . nH2O (M = Nd, Eu), and H2(oep) as starting materials. The compounds adopt a symmetrical triple-decker structure with two outer oep rings and one inner nc ring, which has been confirmed by 'H NMR spectroscopy and X-ray structural determination of the Nd complex. Both compounds give a near-IR absorption at 1021 nm (for M=Nd) or 1101 nm (for M = Eu), which has rarely been observed for neutral (or hole-free) triple-decker complexes and can be ascribed to the lowest-energy Q'(0, 0) transition. Similarly to the double-decker analogues. these triple-decker complexes undergo a series of one-electron transfer processes with a relatively small potential gap (1.1 -1.2 V) between the first oxidation and the first reduction.

Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions

“…Thus, the oxidation of hydrazine to molecular nitrogen has been extensively studied over the past years [79,84,387,[456][457][458][459], and the mechanism and kinetics of hydrazine oxidation have been analyzed under a wide range of conditions, in solution and with several electrodes [460]. Because of the large overpotential of hydrazine at conventional electrodes, one promising approach to minimize overvoltage effects is through the use of an electrocatalytic process at chemically modified electrodes with phthalocyanines [75,80,96,[461][462][463].…”

Synthesis, crystal structure and self-assembly property of a mixed (phthalocyaninato) (porphyrinato) europium triple-decker complex

“…Particularly, to the best of our knowledge, the mixed ring triple-deckers containing one porphyrin ligand are only limited to {(Pc)Eu(Pc)Eu[T(4-OCH 3 )PP)]} [11] and {PcCe[T(4-OCH 3 )PP)]CePc} [12]. As part of our continuing interest in heteroleptic rare earth complexes with tetrapyrrole ligands [13][14][15], we describe herein a systematic study of a mixed phthalocyaninato and porphyrinato triple-decker complex, namely [Eu 2 (Pc) 2 (TClPP)], including their synthesis, crystal structure and self-assembly properties.According to our previously described procedure [13], the target triple-decker complex was obtained from the reaction between corresponding metal free porphyrin H 2 (TClPP) and Eu(Pc) 2 in the presence of Eu(acac) 3 ·nH 2 O in refluxing TCB. Repeated chromatography followed by recrystallization from chloroform/methanol gives pure target compound in good yield of 36%.…”

“…Particularly, to the best of our knowledge, the mixed ring triple-deckers containing one porphyrin ligand are only limited to {(Pc)Eu(Pc)Eu[T(4-OCH 3 )PP)]} [11] and {PcCe[T(4-OCH 3 )PP)]CePc} [12]. As part of our continuing interest in heteroleptic rare earth complexes with tetrapyrrole ligands [13][14][15], we describe herein a systematic study of a mixed phthalocyaninato and porphyrinato triple-decker complex, namely [Eu 2 (Pc) 2 (TClPP)], including their synthesis, crystal structure and self-assembly properties.…”

Toward panchromatic organic functional molecules: Density functional theory study on the nature of the broad UV–Vis–NIR spectra of substituted tetra(azulene)porphyrins

“…This in turn will induce remarkably red-shifted broad Q bands into the NIR region, resulting in complicated electron absorption spectrum of tetra(azulene)porphyrins (TAzPs) relative to most general porphyrins (Pors) [41][42][43], tetraazaporphyrins (TAPs) [43], phthalocyanines (Pcs) [43][44][45][46], naphthalocyanines (Ncs) [47,48], and even many core-modified porphyrins [49][50][51][52][53][54][55][56][57]. In addition, the absorption spectra of some sandwich-type multi(tetarpyrrole) metal multiple-decker complexes can also cover such a broad NIR region [58][59][60][61][62][63][64][65]. However, their absorption intensity in this region is much weaker than TAzPs.…”

“…Introduction of electron-withdrawing or electron-donating groups onto the periphery of TAzP skeleton further tunes the HOMO-LUMO gap, inducing obvious red/blue-shift of the NIR electronic absorption bands of H 2 [␣-(NH 2 ) 4 TAzP]/H 2 [-(NH 2 ) 4 TAnP] into the range of 1000-2500 nm. Moreover, in combination with the previous results [22,[25][26][27][28][29][30][58][59][60][61][62][63][64][65], general rule regarding the design of panchromatic organic functional molecules is also proposed.…”