π–π Aggregation in metalloporphyrins: causative factors

Abraham, Raymond J.; Eivazi, Fahimeh; Pearson, Harry; Smith, Kevin M.

doi:10.1039/c39760000699

Cited by 71 publications

(45 citation statements)

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“…The reactions were carried out by refluxing an ethanolic solution of the 3,4-disubstituted pyrrole with an excess of formaldehyde and a strong acid such as hydrobromic acid. 15 The resulting macrocycles were then air oxidised to the corresponding porphyrins over a period of a week. Slow oxidation gives better yields than procedures involving bubbling air through the reaction mixture.…”

Section: Resultsmentioning

confidence: 99%

“…Essentially all of the observed peaks from the solid S phase can be indexed as (hk) reflections arising from a 2-D square lattice, with a lattice parameter a increasing from 20.6 Å for the C 8 compound, to 24.5 Å for the 10 C 12 derivative, with only a wide-angle peak at approximately 4.5 Å being associated with the periodicity of the stacking along the columns. From these data we are strictly speaking unable to determine whether the columns are completely untilted with respect to the x-y plane of the square lattice 15 (tetragonal symmetry) or slightly tilted (monoclinic symmetry). In the latter case reflections such as (100) and (010) etc.…”

Section: X-ray Diffractionmentioning

confidence: 99%

“…Initially, nuclei formed that developed into 15 dendritic or flower-like textures, observed for the C 8 and C 10 porphyrin compounds respectively (Figures 1(a) and 1(b)), both of which have previously been reported for hexagonal ordered columnar phases 23 . The C 12 Zn compound displayed a spherulitic texture (Figure 1(c)), which is also characteristic 20 of a columnar phase 16,24 .…”

mentioning

confidence: 99%

“…The mesophase behaviour of both metallated and free-base octa-β-substituted porphyrins has been examined for a variety of substituent groups. The metallated compounds have generally been found to display much more diverse liquid-50 crystalline phase behaviour due to the stronger electrostatic interactions between the porphyrin rings, which can be considered as negatively charged due to the delocalised π electron systems, and the positively charged metal cores of neighbouring porphyrins 15 . Interestingly, the stabilisation of 55 liquid crystalline mesophases has also been achieved by decreasing the symmetry of the discotic molecules, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and phase behaviour of β-octaalkyl porphyrins

et al. 2009

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A homologous series of three octakis-alkyl-substituted porphyrin (OAP) derivatives with alkyl chain lengths of C 8 , C 10 and C 12 has been synthesised. For each compound, both the free-base (i.e. two H-atoms) and the fourfold coordinated zinc complex were investigated, where the latter for each chainlength was found to exhibit liquid crystalline mesophase behaviour. At low temperatures 10 all three metal coordinated compounds formed a solid S phase with a structure based on a square packing of columns with a stacking periodicity of 4.7 Å. At increased temperatures the square packed solid S phases undergo phase transitions to liquid-crystalline columnar phases based on centered rectangular lattices of C2/m symmetry, with the ratio of the lattice parameters, a/b, ranging between 1 and 1.732. The a/b ratio exhibited two discontinuous jumps with increasing 15 temperature prior to melting to the isotropic phase for Zn-OAP-C 8, implying the existence of three columnar phases denoted Col r1 , Col r2 and Col r3 . For the longer chainlength compounds, the number of mesophases formed was reduced, first to two for Zn-OAP-C 10 , then to one for Zn-OAP-C 12 .

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Section: Resultsmentioning

confidence: 99%

Section: X-ray Diffractionmentioning

confidence: 99%

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confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis and phase behaviour of β-octaalkyl porphyrins

et al. 2009

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“…This was attributed to π-π aggregation which is a well known phenomenon for metalloporphyrins. 27 1 H NMR studies on metalloporphyrins reported in the literature demonstrated that the strength of aggregation is dependent on the interaction of the metal ion with the porphyrin π-system. The aggregation was enhanced by the presence of electron-withdrawing substituents on the porphyrin periphery.…”

Section: Synthesismentioning

confidence: 99%

Nonlinear absorption properties of 5,10-A2B2porphyrins—correlation of molecular structure with the nonlinear responses

Zawadzka

Wang

Blau

et al. 2013

Photochem Photobiol Sci

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The nonlinear absorption properties of two series of novel free base and metalated meso 5,10-A 2 B 2 substituted porphyrins, both bearing p-tolyl as an A substituent and TMS-ethynyl or bromine as a B substituent, were investigated with the open Z-scan technique at 532 nm in the ns time regime. Most of the compounds exhibited a transmission drop with increasing input fluence. This behavior is desirable for their applications in optical limiting. More complex responses: a drop in transmission followed by an increase in transmission or an increase in transmission followed by a transmission drop, with increasing input fluence, were detected for certain compounds. All of the recorded responses were successfully fitted with a four-level model with simultaneous two-photon absorption arising from the higher excited states (consecutive one-+ one-+ two-photon absorption). The TMS-ethynyl group was found to be a more efficient meso substituent in optical limiting than the bromine atom. Indium, lead and zinc complexes with TMS-ethynyl substituents were the strongest positive nonlinear absorbers amongst compounds studied which makes them the most interesting candidates for optical limiting application.

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Synthesis and Mesogenic Properties of Porphyrin Octaesters

et al. 1999

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A new and efficient method of preparing 3,4‐pyrrolediacetic esters 3 is reported, together with their conversion, according to the Lindsey procedure, to a series of octa‐ and dodeca‐substituted porphyrins. This procedure, which consists of a palladium‐catalysed oxidative alkoxycarbonylation of N‐substituted dipropargylamine derivatives 1, works nicely for n‐alkyl alcohols in the range C1 to C14. The thermotropic behaviour of this series of porphyrins (28 compounds) has been investigated using polarization microscopy, DSC, X‐ray diffraction, and miscibility tests. The planarity of the macrocyclic core constitutes the major structural requirement for mesophase formation. The mesophase temperature range is controlled by the length of the side chains through the melting point and by the strength of π‐π interactions among the cores through the clearing point. The same set of rules governing porphyrin packing in the solid state can be employed to predict mesophase formation and organization in porphyrin octaesters

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π–π Aggregation in metalloporphyrins: causative factors

Cited by 71 publications

References 0 publications

Synthesis and phase behaviour of β-octaalkyl porphyrins

Synthesis and phase behaviour of β-octaalkyl porphyrins

Nonlinear absorption properties of 5,10-A2B2porphyrins—correlation of molecular structure with the nonlinear responses

Synthesis and Mesogenic Properties of Porphyrin Octaesters

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