Showing papers on "Porphyrin published in 1997"
TL;DR: In this paper, the first detection and characterization of oxomanganese(V) porphyrin complexes under ambient catalytic conditions is described, and the Soret maximum of 1 was found at 443 nm, intermediate between that of oxOManganese (IV) (428 nm) and Mn(III)TMPyP (462 nm), thus facilitating its detection.
Abstract: The first detection and characterization of oxomanganese(V) porphyrin complexes under ambient catalytic conditions is described. The reaction of (tetra-(N-methylpyridyl)porphyrinato)manganese(III) [Mn(III)TMPyP] with a variety of oxidants such as m-chloroperoxybenzoic acid (m-CPBA), HSO5-, and ClO- has been shown to produce the same, short-lived intermediate (1) by stopped-flow spectrophotometry. The Soret maximum of 1 was found at 443 nm, intermediate between that of oxomanganese(IV) (428 nm) and Mn(III)TMPyP (462 nm), thus facilitating its detection. The rate of formation of 1 from Mn(III)TMPyP followed second-order kinetics, first order in Mn(III) porphyrin and first order in oxidant. The rate constants have the following order: m-CPBA (2.7 × 107 M-1 s-1) > HSO5- (6.9 × 105 M-1 s-1) ≈ ClO- (6.3 × 105 M-1 s-1). Once formed, the intermediate species 1 was rapidly converted to oxoMn(IV) (2) by one-electron reduction with a first-order rate constant of 5.7 s-1. The oxoMn(IV) species 2 was relatively stabl...
394 citations
TL;DR: In this article, a real-space conformational analysis of individual porphyrin molecules using scanning tunnelling microscopy was performed on corrugated gold surfaces and two different conformations were identified as precursory (metastable) and final states of adsorption.
Abstract: The structure and conformation of a molecule determine its chemical and physical properties. Molecular conformation at interfaces is of particular importance in organic thin films1: in organic optoelectronic devices2,3, for example, charge carrier injection is influenced by interfacial properties4. Here we present a real-space conformational analysis of individual porphyrin molecules using scanning tunnelling microscopy5,6. Porphyrins have been used as model systems to study charge transfer7 and in vivo photoactivation of drug precursors8, and have also been used in organic light-emitting diodes9. We find that changes in the porphyrins' conformation occur predominantly by rotations around the bonds to four tertiary butyl appendages, which differ on different metal substrates. On corrugated gold (110) surfaces, we identify two different conformations as the precursory (metastable) and final states of adsorption. This kind of conformational adaptation to a surface may be general for adsorbed organic molecules, and might have important consequences for the technological applications of organic thin films.
374 citations
366 citations
TL;DR: In this paper, the authors performed density functional theory (DFT) calculations of iron−porphyrin and its complexes with O2, CO, NO, and imidazole (Im).
Abstract: We have performed density functional theory (DFT) calculations of iron−porphyrin (FeP) and its complexes with O2, CO, NO, and imidazole (Im). Our fully optimized structures agree well with the available experimental data for synthetic heme models. Comparison with crystallographic data for proteins highlights interesting features of carbon monoxymyoglobin. The diatomic molecule induces a 0.3−0.4 A displacement of the Fe atom out of the porphyrin nitrogen (Np) plane and a doming of the overall porphyrin ring. The energy of the iron−diatomic bond increases in the order Fe−O2 (9 kcal/mol) < Fe−CO (26 kcal/mol) < Fe−NO (35 kcal/mol). The ground state of FeP(O2) is an open shell singlet. The bent Fe−O2 bond can be formally described as FeIII−O2-, and it is characterized by the anti-ferromagnetic coupling between one of the d electrons of Fe and one of the π* electrons of O2. FeP(CO) is a closed shell singlet, with a linear Fe−C−O bond. The complex with NO has a doublet ground state and a Fe−NO geometry intermed...
352 citations
Journal Article•
TL;DR: Esterified ALAs are new and promising drugs for use in photochemotherapy of cancer and high-performance liquid chromatography and fluorescence microscopic studies indicated that esterification of ALA has neither impact on the fluorescing porphyrin species formed nor impact on their intracellular localization.
Abstract: Human tumor cells of the lines WiDr (adenocarcinoma of the rectosigmoid colon), NHIK 3025 (carcinoma of the cervix), and V79 Chinese hamster fibroblasts were treated with 5-aminolevulinic acid (ALA) and ALA esterified to C1-C3 and C6-C8 chained aliphatic alcohols (ALA-esters). In the human cell lines, esterification of ALA with the long-chain (C6-C8) alcohols was found to reduce 30-150-fold the amount of ALA needed to reach the same level of protoporphyrin IX (PpIX) accumulation as with non-esterified ALA. The long-chained ALA-esters were less efficient in stimulating PpIX formation in V79 cells, i.e., the same amount of PpIX was formed by a 1-2.6-fold lower concentration of long-chained ALA-esters than with ALA. Short-chained ALA-esters (C1-C3) induced 5 to 10 times lower PpIX accumulation than ALA in all of the cell lines. High-performance liquid chromatography and fluorescence microscopic studies indicated that esterification of ALA has neither impact on the fluorescing porphyrin species formed nor impact on their intracellular localization. The PpIX formed from ALA-esters and ALA was found to be equally efficient in sensitizing cells to photoinactivation. The present results indicate that esterified ALAs are new and promising drugs for use in photochemotherapy of cancer.
269 citations
250 citations
TL;DR: Selective Localization of Photosensitizers in Tumors: A Review of the Phenomenon and Possible Mechanisms and Strategies for Tumor Targeting by Photodynamic Sensitizers.
224 citations
Journal Article•
189 citations
TL;DR: Ruthenium(II) is a stable catalyst for alkene oxidation by tert-butyl hydroperoxide with high product turnover this article, and is used in this article.
184 citations
TL;DR: In this paper, the photo-oxidation of phenol and 2-, 3- and 4-monochlorophenols by irradiation with visible light in aqueous alkaline solution in the presence of photosensitizers and oxygen is described.
Abstract: The photo-oxidation of phenol and 2-, 3- and 4-monochlorophenols by irradiation with visible light in aqueous alkaline solution in the presence of photosensitizers and oxygen is described. The reactions were carried out in the absence or presence of detergents. The photosensitizers used were Al(III), Zn(II) and Ga(III) complexes of 2,9,16,23-tetrasulphophthalocyanine (1a–1c), 5,10,15,20-tetrakis(4-carboxy-phenyl)porphyrin (2), a cationically charged perylene tetracarboxylic acid diimide (3), rose bengal (4) and methylene blue (5). The photosensitizers exhibit different activities and photo-oxidative stabilities which are strongly dependent on the pH, hydrolysis sensitivity and aggregation tendency. Singlet oxygen, obtained by photoinduced energy transfer from the excited photosensitizers, dominates the initial steps of photo-oxidation. A reaction sequence is proposed on the basis of the identification of carbon dioxide and maleic or fumaric acid as the products of photo-oxidation in the absence of detergent and the evaluated mass balances.
182 citations
TL;DR: A cytochrome c oxidase model that consists of a cobalt(II) porphyrin with a copper(I) triazacyclononane macrocycle fastened on the distal face and an imidazole covalently attached to the proximal face has been synthesized and characterized.
Abstract: A cytochrome c oxidase model that consists of a cobalt(II) porphyrin with a copper(I) triazacyclononane macrocycle fastened on the distal face and an imidazole covalently attached to the proximal face has been synthesized and characterized. Redox titrations with molecular oxygen (O2) and cobaltocene were carried out, and O2 was found to bind irreversibly in a 1:1 ratio to the model compound. This O2 adduct (a bridged peroxide) can be fully reduced to the deoxygenated form with four equivalents of cobaltocene. The model compound was adsorbed on an edge-plane graphite electrode, and rotating ring-disk voltammetry was used to monitor the electrocatalytic reduction of O2. Four-electron reduction of O2 was observed at physiological pH.
TL;DR: In this article, 1H NMR and UV−vis spectroscopic studies of 5-phenyl-10,15,20-tris[4-(N-methyl)pyridinium]porphyrin (TMPyP(4)) in water were carried out.
Abstract: There has been a controversy about the self-aggregation of 5,10,15,20-tetrakis[4-(N-methyl)pyridinium]porphyrin (TMPyP(4)) in water. In order to make clear whether TMPyP(4) forms a dimer in water, 1H NMR and UV−vis spectroscopic studies of 5-phenyl-10,15,20-tris[4-(N-methyl)pyridinium]porphyrin (TriMPyP), 5,10-diphenyl-15,20-bis[4-(N-methyl)pyridinium]porphyrin (5,10-DiMPyP), and 5,15-diphenyl-10,20-bis[4-(N-methyl)pyridinium]porphyrin (5,15-DiMPyP) have been carried out. The 1H NMR spectra indicate the formation of the self-aggregates of these phenylpyridiniumporphyrins in D2O when the porphyrin concentration is 1 × 10-3 M. Comparison of the 1H NMR spectra of TMPyP(4) with those of TriMPyP and DiMPyPs clearly exhibits that TMPyP(4) does not form its dimer in D2O. Broadening of the signal due to the β-pyrrole protons of the cationic porphyrin is ascribed to the tautomerism of the inner N-D deuterons with the rate slower than that of the N-H protons. At lower concentrations (∼10-5 M), both DiMPyP's form di...
TL;DR: In this paper, a columnar structure for tetrakis(3,5'-dihydroxyphenyl)porphyrin and its derivatives was found, where the position of the peripheral hydroxyl groups, the choice of metallo- or free base porphyrin, and the nature of the solvate dramatically influence structural features.
Abstract: Symmetrically substituted octahydroxy porphyrins, tetrakis(3',5'-dihydroxyphenyl)porphyrin, H2T(3',5'- DHP)P, tetrakis(2',6'-dihydroxyphenyl)porphyrin, H2T(2',6'-DHP)P, and their Zn(II) and Mn(III) derivatives have been developed as building blocks for supramolecular hydrogen-bonded networks. The crystal structures of a series of these porphyrins exhibit unique structural features through assembly of porphyrin networks by means of directional hydrogen bonding. The position of the peripheral hydroxyl groups, the choice of metallo- or free base porphyrin, and the nature of the solvate (i.e., guest) dramatically influence structural features. A one-dimensional, columnar structure is found for H2T(3',5'-DHP)P‚5EtOAc. With benzonitrile as solvate, the structure of H2T(3',5'-DHP)P‚7C6H5- CN changes substantially to a three-dimensional corrugated-sheet structure in order to accommodate a larger pore size. When the hydroxyl substituents are simply changed from the m- to the o-phenyl positions, an essentially two-dimensional layered structure is formed for H2T(2',6'-DHP)P‚4EtOAc. Zn(T(2',6'-DHP)P)(EtOAc)2‚2EtOAc has a two-dimensional layered structure, similar to that of its free base H 2T(2',6'-DHP)P interaction between the aryl rings of the adjacent layers. The crystal structures of both Zn(T(3 ',5'-DHP)P) and Mn(T(3',5'-DHP)P)(Cl) exhibited three-dimensional hydrogen-bonding features. Zn(T(3',5'-DHP)P)(THF)2‚2THF‚3CH2Cl2 has a three-dimensional interconnected layered structure with metalloporphyrins arranged in a slipped stack orientation within the layers. In the structure of Mn(T(3',5'-DHP)P)(THF)2‚Cl‚2THF‚5C6H5CH3, a chloride anion dictates the three-dimensional packing by bridging four metalloporphyrin molecules through Cl‚‚‚HO bonding interactions. In all of these structures, large solvate-filled channels are present with cross-sections as large as 42 A 2 . The pore volumes of these channels are exceptionally large: as much as 67% of the unit cell volume.
TL;DR: A strategy for constructing porphyrin–electron acceptor pairs via specific interactions and the evaluation of ET in the respiratory system and noncovalently linked complexes is focused on.
Abstract: In the respiratory system, electron carriers such as ubiqui-none and cytochrome c play an important role in the electron transfer (ET) reaction between oxidoreductases embedded in the mitochondrial membrane. This review focuses on a strategy for constructing porphyrin–electron acceptor pairs via specific interactions and the evaluation of ET in these systems. Particularly, the molecular recognition of ubiqui-none analogues by porphyrin host molecules and the mimicking of protein–protein complexation using myoglobin reconstituted with a synthetic porphyrin are reviewed, and the characteristics of the photoinduced ET within noncovalently linked complexes are discussed.
TL;DR: A review of recent research papers in the field of Chl and BChl biosynthesis appearing since the last review on Chl in this journal in 1993 by Senge (5) can be found in this paper.
Abstract: One of the most vigorous areas of photobiological research is concerned with the elucidation of the structure and biosynthesis of chlorophylls (Ch1s)t and bacteriochlorophylls (BChls) and their incorporation into pigment-protein complexes for both the harvesting and transduction of solar energy for photosynthesis. The keen interest in the formation of Chls and other natural tetrapyrrole pigments is reflected by the many recent reviews including Battersby and Leeper (I), Scheer ( 2 ) , Jordan (3), Deisenhofer and Noms (4), Senge (5 ) , Bryant (6), Chadwick and Ackrill (7), Blankenship et al. (8), Battersby (9) and Avissar and Moberg (10). This review concentrates on recent research papers in the field of Chl and BChl biosynthesis appearing since the last review on Chl in this journal in 1993 by Senge (5). An attempt is made to integrate this recent research on specific aspects of Chl biosynthesis into our understanding of the entire pathway. Much is known about the biosynthesis of the tetrapyrrole chromophores of Chls u and b, the major Chl-protein complexes of higher plants and algae; however, the biosyntheses of many of the Chls c of the chromophyte algae (1 1) and of many of the known BChls of the photosynthetic bacteria (2) still require investigation. Only partially understood, however, is the manner of the
TL;DR: In this paper, the crystal structures of three porphyrin diacid species, [H4OEP]-ClO4)2,[H4TMP]-CLO4]2 and [H 4TMP]2+ have been determined from low-temperature X-ray diffraction data to delineate how the peripheral substituents of the porphrin affect the overall molecular flexibility.
Abstract: The crystal structures of three porphyrin diacid species, [H4OEP](ClO4)2, [H4TPP](ClO4)2, and [H4TMP](ClO4)2, have been determined from low-temperature X-ray diffraction data to delineate how the peripheral substituents of the porphyrin affect the overall molecular flexibility. [H4OEP](ClO4)2 (|Cb| = 0.46 A), [H4TMP](ClO4)2 (|Cb| = 0.67 A, molecule 1), and [H4TPP](ClO4)2 (|Cb| = 0.93 A) show increasingly saddled core conformations with effective D2d symmetry. The mean porphyrin−aryl group dihedral angles in [H4TPP](ClO4)2 and [H4TMP](ClO4)2 (molecule 1) are 27(2)° and 63(13)°, respectively. The steric bulk of the mesityl substituents in [H4TMP]2+ limits the range of observed porphyrin−aryl group dihedral angles to >50° and, consequently, the magnitude of the core distortion. [H4TMP]2+ is therefore less flexible than [H4TPP]2+. Molecular mechanics calculations, using a modified version of MM2(87) and a newly developed force field for porphyrin diacids, correctly predict that the flexibility of meso-tetraar...
TL;DR: In this paper, three metal complexes of homochiral porphyrin were investigated as catalysts for enantioselective epoxidation of unfunctionalized olefins under various reaction conditions.
Abstract: Three metal complexes of one particular homochiral porphyrin were investigated as catalysts for enantioselective epoxidation of unfunctionalized olefins under various reaction conditions. Much better results were obtained with the iron and ruthenium complexes than with the manganese derivative. The absence of any effect of amines on the iron porphyrin-catalyzed reaction in benzene, as well as the superior results in aromatic as opposed to both more and less polar nonaromatic solvents, suggest that specific association of aromatic molecules to the metalloporphyrin affects its solution structure. Strong evidence for the involvement of active oxidants that are more selective than trans-dioxoruthenium(VI) porphyrin is provided by the significant effect of primary oxidants on the ruthenium porphyrin-catalyzed reactions. Preliminary results with the iron complex of an only slightly modified porphyrin under the optimized reaction conditions found in this study resulted in epoxidation of styrene and 4-chlorostyre...
TL;DR: Compound I of Proteus mirabilis and bovine liver catalases (PMC and BLC) were studied combining EPR spectroscopy and the rapid-mix freeze-quench techniques, showing that the porphyrin pi-cation radical disappears and, instead, a tyrosyl radical is formed.
Abstract: Compound I of Proteus mirabilis and bovine liver catalases (PMC and BLC, respectively) were studied combining EPR spectroscopy and the rapid-mix freeze−quench techniques. Both enzymes, when treated with peroxyacetic acid, form a catalytic intermediate which consists of an oxoferryl porphyrin π-cation radical. In PMC this intermediate is semistable, and an unexpected reversible equilibrium under pH influence takes place between two forms of compound I with different coupling between the oxoferryl and the porphyrin π-cation radical. At acid pH, one form has a ferromagnetic character as in Micrococcus luteus compound I. At neutral pH, another form with a much smaller coupling, reminiscent of the horse radish peroxidase compound I, is detected. The approximate midpoint, estimated for these changes in the range 5.3 < pH < 6.0, approaches the pKa value of an histidyl residue. The residues possibly involved in the transformation are discussed in terms of the known structure of PMC compound I. The EPR spectrum of...
TL;DR: In this article, bromination on the pyrroles was explored as a means of increasing the redox potentials and the catalytic activities of the copper and manganese complexes of a cationic porphyrin.
TL;DR: In aqueous solutions, the FeIP state is relatively stable for the tetrakis(N-methyl-2-pyridyl)porphyrin at high pH but is shorter lived in neutral and acidic solutions as discussed by the authors.
Abstract: Several iron porphyrins have been reduced by photochemical and radiation chemical methods, in organic solvents and in aqueous solutions, from FeIIIP to FeIIP to FeIP and beyond. In aqueous solutions, the FeIP state is relatively stable for the tetrakis(N-methyl-2-pyridyl)porphyrin at high pH but is shorter lived in neutral and acidic solutions. The FeIP state of tetrakis(N-methyl-3-pyridyl)porphyrin and tetrakis(N-methyl-4-pyridyl)porphyrin are short-lived at any pH. Decay of FeIP is accelerated by H+ and by CO2, probably via reaction with the Fe0P state formed upon disproportionation of FeIP. These reactions may lead to formation of H2 and CO, respectively, and to formation of the chlorin, FeIIPH2, as a side product. The FeIP state is also observed as a stable product in several organic solvents. This is observed by photolysis of iron tetraphenylporphyrin and several of its derivatives (e.g., trimethyl-, dichloro- and pentafluorophenyl), mainly in dimethylformamide and acetonitrile solutions, using triet...
TL;DR: In this article, the authors studied iron porphyrin complex-catalyzed oxygenation of hydrocarbons by several oxidants (i.e., hydrogen peroxide, tert-butyl hydroperoxide, and m-chloroperoxybenzoic acid (MCPBA)) in the presence of H218O.
Abstract: We have studied iron porphyrin complex-catalyzed oxygenations of hydrocarbons by several oxidants (i.e., hydrogen peroxide, tert-butyl hydroperoxide, and m-chloroperoxybenzoic acid (MCPBA)) in the presence of H218O. In the olefin epoxidation and alkane hydroxylation reactions catalyzed by (meso-tetrakis(pentafluorophenyl)porphinato)iron(III) chloride [Fe(F20TPP)Cl], the percentages of 18O incorporated into the oxygenated products were found to be the same in all of the reactions of hydrogen peroxide, tert-butyl hydroperoxide, and MCPBA, leading us to conclude that a common high-valent iron oxo complex was the reactive intermediate responsible for oxygen atom transfer. When the epoxidation of cyclooctene by MCPBA and H2O2 was performed at low temperature in the presence of H218O, it was found that there was no 18O-incorporation from labeled water into cyclooctene oxide. We interpreted the lack of 18O-incorporation in these reactions with that an electronegatively-substituted iron porphyrin complex forms a ...
TL;DR: In this paper, the porphyrin-C60 dyads were synthesized using a protection-deprotection sequence by coupling of monoprotected diols with 1,5 followed by EDCmediated coupling6,7 with 5-(4′-carboxyphenyl)-10,15,20-triphenylporphine (3, Scheme 2).
Abstract: The unique photophysical properties of C60 have generated significant research focused on its use as the acceptor in covalently bound donor-acceptor pairs.1 In particular, photophysical properties of porphyrin-linked C60 hybrids have received considerable attention.2 It has been shown that intramolecular electron transfer from the porphyrin to C60 to generate ion pairs occurs extremely rapidly with zinc porphyrins and with free base dyads in polar solvents; in nonpolar solvents, efficient formation of C60* was seen.2a,g,3 The extent of such interactions in the ground state has been attributed to the rigid conformation enforced by the linker.2,3 Herein we report the efficient synthesis as well as computational and photophysical studies of two novel classes of porphyrin-C60 hybrids. These hybrids (i.e., dyads) are unique in that (i) their synthesis utilizes a convergent strategy, providing access to a rich array of new structures, including the first azalinked porphyrin-fullerene hybrid, (ii) despite the fact that the porphyrin moiety is not rigidly connected to C60, electronic interactions still occur in the ground state, and (iii) cations induce formation of a complex with open-chain crown-ether mimics 6 and 8 in which there is a dynamic equilibrium between complexed and uncomplexed states (see Scheme 1). In the former state, the two chromophores are brought closer together, significantly increasing intramolecular interactions. Armed with a facile high-yield route to carboxylic acid 1 via sulfonium ylide addition and subsequent hydrolysis,4 fullerenes possessing linkers with terminal hydroxyl groups were synthesized through a protection-deprotection sequence by coupling of monoprotected diols with 1,5 followed by EDCmediated coupling6,7 with 5-(4′-carboxyphenyl)-10,15,20-triphenylporphine (3, Scheme 2).7,8 Flexibility in the choice of the
TL;DR: In this article, self-assembly and non-covalent interactions are employed for the preparation of a new family of cationic artificial supramolecular======multiporphyrin aggregates.
TL;DR: Ruthenium porphyrin and porphycene complexes catalyse stereospecificcyclopropanation of styrenes; high product turnover with up to 90.8% ee======
TL;DR: In this article, a joint experimental and theoretical investigation of the linear and nonlinear optical response of butadiyne-linked zinc porphyrin oligomers is presented, and the assignment of the observed linear and photoinduced absorption features is supported by a Configuration Interaction description of the singlet and triplet excited states.
Abstract: We present a joint experimental and theoretical investigation of the linear and nonlinear optical response of butadiyne-linked zinc porphyrin oligomers. Efficient overlap between the chromophores leads to a large red-shift of the Q absorption band together with a splitting of the B band into two components when increasing the chain length from one to two repeating porphyrin units. Ultrafast pumb-probe measurements performed on these compounds show several well-defined features, associated with singlet excited state absorption. We also find clear evidence for the formation of longer-lived triplet excitons, resulting from very efficient singlet–triplet intersystem crossing processes. For the monomers, the assignment of the observed linear and photoinduced absorption features is supported by a Configuration Interaction description of the singlet and triplet excited states. In the case of the porphyrin dimer, agreement with the experimental results can only be obtained by considering a sizable cumulenic contr...
TL;DR: Spectrosopic studies suggest that conformations similar to those determined by X-ray crystallography are present in solution for the 5,15-dialkyl- and 5, 15-diaryl-substituted porphyrins.
Abstract: Conformational analysis of highly substituted porphyrins has potential implications for modeling the behavior of macrocycles in tetrapyrrole-containing protein complexes and during catalytic reactions. In order to study the influence of different substituent patterns on the conformation of the porphyrin macrocycle, a series of metal free and nickel(II) decasubstituted porphyrins bearing aryl or ethyl groups at opposite meso positions and alkyl groups at the pyrrole positions have been synthesized and characterized by X-ray crystallography. Crystal structures of the free-base porphyrins with 5,15-diaryl substituents showed negligible out-of-plane distortion but a large amount of in-plane distortion along the 5,15-axis accompanied by large bond angle changes similar to those previously seen for related porphyrins with 5,15-dialkyl substituents. Nickel(II) complexes of the 5,15-diaryl-substituted porphyrins show planar or modestly nonplanar conformations, suggesting that these complexes are not intrinsically...
TL;DR: In this paper, the reaction of the iron(II) picket fence porphyrin derivative [Fe(TpivPP)(NO2] with NO has been examined.
Abstract: The reaction of the iron(II) picket fence porphyrin derivative [Fe(TpivPP)(NO2)]- (Nasri et al. J. Am. Chem. Soc. 1991, 113, 717) with NO has been examined. The result is a new hexacoordinated iron...
TL;DR: Porphyrin dimers linked in the meso-positions by bridges containing alkynes conjugated with the porphrin π-systems display highly perturbed electronic absorption spectra as discussed by the authors.
Abstract: Porphyrin dimers linked in the meso-positions by bridges containing alkynes conjugated with the porphyrin π-systems display highly perturbed electronic absorption spectra. We have prepared a series...