Lanthanide-Porphyrin Hybrids: from Layered Structures to Metal–Organic Frameworks with Photophysical Properties

Abstract

Rare-earth layered hydroxides with intercalated tetrasulfonated porphyrins and corresponding to the chemical formula Ln2(OH)4.7(Por)0.33·2H2O (Ln = Eu(3+), Tb(3+); Por = 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and PdTPPS) have been prepared to investigate their photophysical properties. A slight variation of the synthetic procedure led to the metal-organic framework (MOF) assembled from a distorted octahedral oxometalate clusters [Eu6(μ6-O)(μ3-OH)8(H2O)14](8+). These secondary building units (SBUs) are linked together by six distorted porphyrin units. During activation, the original SBU loses not only water molecules from the coordination sphere but also the central μ6-O atom. The loss of the central atom results in the distortion of the octahedral [Eu6(μ6-O)(μ3-OH)8(H2O)14](8+) SBU into a trigonal antiprismatic [Eu6(μ3-OH)8(H2O)2](10+) SBU with two μ3-OH groups nearly in plane with the europium atoms and the reduction of pores to approximately 2 × 3 Å. As a result, the MOF has no accessible porosity. This transformation was thoroughly characterized by means of single-crystal X-ray crystallographic analysis of both phases. Solid-state photophysical investigations suggest that the MOF material is fluorescent; however, in contrast to the prepared layered hydroxides, the as-prepared MOF is an effective sensitizer of singlet oxygen, O2((1)Δg), with a relatively long lifetime of 23 ± 1 μs. The transition is also accompanied by variation in photophysical properties of the coordinated TPPS. The alteration of the fluorescence properties and of the O2((1)Δg) lifetime presents an opportunity for preparation of MOFs with oxygen-sensing ability or with oxidation potential toward organic molecules by O2((1)Δg).

Layered Hydroxide–Porphyrin Hybrid Materials: Synthesis, Structure, and Properties

“…[24] In addition, the intensity of the Q(0,1) band increases at the expense of the Q(0,0) band ( Figure 6) and two fluorescence lifetimes that characterize fluorescence decay curves are shortened as the loading of TPPS molecules in the LDH film is increased. [35] In the latter case, time-resolved fluorescence spectroscopy showed that the dominance of the (0,1) fluorescence band is accompanied by considerable shortening of TPPS fluorescence lifetimes. [35] In the latter case, time-resolved fluorescence spectroscopy showed that the dominance of the (0,1) fluorescence band is accompanied by considerable shortening of TPPS fluorescence lifetimes.…”

“…The results for the films are similar to those reported for Mg 2 Al-LDH-PdTPPC, [29] Zn R Al-LDH-ZnTPPS and Mg R Al-LDH-TPPS (R = 2 or 4), [13,29,30] and Zn R Al-LDH-PdTPPC (R = 2 or 4) [31] hybrids ( Figure 5). [35] The observations that extensive porphyrin π-π stacking does not take place within the LH interlayer space are good prerequisites for the fabrication of photoactive polymer composites. [31] In addition, aggregation was not indicated for Zn 3 Al-LDH-Ti-OTPPS, [18] LiAl 2 -LDH-ZnTPPC, [32] or for nanoordered LDH films prepared by a layer-by-layer technique with assembled TPPC [33] and ZnPcS.…”

“…[34] In some cases, broadening of the Soret bands might be attributed to a closer packing of the porphyrin moieties in the interlayer of the LZH salts [21] and LREH (RE = Eu III , Tb III ). [35] The observed spectral changes can be attributed to strong interactions between the periphery of individual molecules and the densely packed hydroxide layers through a range of different orientations of the porphyrin molecules relative to each other and with respect to the hydroxide layers. [31,36] [24] and (c) Zn 2 Al-PdTPPC powder.…”

Photophysical and electrochemical properties of a novel lanthanide tetra(4-sulfonatophenyl)porphyrin

“…To our knowledge, many free-based porphyrins such as TCPP (tetrakis(4-carboxyphenyl)porphyrin), TCMOPP (tetrakis(4-(carboxymethyleneoxy)phenyl)porphyrin), TDCPP (tetrakis(3,5-dicarboxyphenyl)porphyrin), and TPyP (mesotetra(4-pyridyl)porphyrin) have been applied to prepare new compounds [6,7]. However, amongst the known compounds, H 2 TPPS (tetra(4-sulfonatophenyl)porphyrin)-containing compounds are rare and only several examples have been reported thus far [8,9]. Lanthanide complexes have also gained more and more interest due to their abundant properties such as magnetism and photoluminescence [10,11] and, nowadays, a great number of lanthanide complexes have been documented [12][13][14].…”

Porphyrin polymers and organic frameworks

“…The MOF also shows the ability to produce long-lived singlet O 2 , and it is proposed as a promising material as a bactericide, oxygen sensor or photo-oxidation catalyst. 88 Burnett et al report that it is possible to exchange bridging linkers in MOF structures. Two-dimensional MOFs were originally created with TCPP and Zn(NO 3 ) 2 then bridged into layered structures wileyonlinelibrary.com/journal/pi ′ -bipyridine showed that the bipyridine ligand can diffuse into the structure and displace the existing linkers, while retaining crystallinity of the new MOF.…”