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Hood D, Sahin T, Parkes‐Loach PS, Jiao J, Harris MA, Dilbeck P, Niedzwiedzki DM, Kirmaier C, Loach PA, Bocian DF, Lindsey JS, Holten D. Expanding Covalent Attachment Sites of Nonnative Chromophores to Encompass the C‐Terminal Hydrophilic Domain in Biohybrid Light‐Harvesting Architectures. CHEMPHOTOCHEM 2018. [DOI: 10.1002/cptc.201700182] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Liu R, Liu M, Hood D, Chen CY, MacNevin CJ, Holten D, Lindsey JS. Chlorophyll-Inspired Red-Region Fluorophores: Building Block Synthesis and Studies in Aqueous Media. Molecules 2018; 23:molecules23010130. [PMID: 29320445 PMCID: PMC6017558 DOI: 10.3390/molecules23010130] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 01/04/2018] [Accepted: 01/06/2018] [Indexed: 02/04/2023] Open
Abstract
Fluorophores that absorb and emit in the red spectral region (600-700 nm) are of great interest in photochemistry and photomedicine. Eight new target chlorins (and 19 new chlorins altogether)-analogues of chlorophyll-of different polarities have been designed and synthesized for various applications; seven of the chlorins are equipped with a bioconjugatable tether. Hydrophobic or amphiphilic chlorins in a non-polar organic solvent (toluene), polar organic solvent (DMF), and aqueous or aqueous micellar media show a sharp emission band in the red region and modest fluorescence quantum yield (Φf = 0.2-0.3). A Poisson analysis implies most micelles are empty and few contain >1 chlorin. Water-soluble chlorins each bearing three PEG (oligoethyleneglycol) groups exhibit narrow emission bands (full-width-at-half maximum <25 nm). The lifetime of the lowest singlet excited state and the corresponding yields and rate constants for depopulation pathways (fluorescence, intersystem crossing, internal conversion) are generally little affected by the PEG groups or dissolution in aqueous or organic media. A set of chlorin-avidin conjugates revealed a 2-fold increase in Φf with increased average chlorin/avidin ratio (2.3-12). In summary, the chlorins of various polarities described herein are well suited as red-emitting fluorophores for applications in aqueous or organic media.
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Hu G, Kang HS, Mandal AK, Roy A, Kirmaier C, Bocian DF, Holten D, Lindsey JS. Synthesis of arrays containing porphyrin, chlorin, and perylene-imide constituents for panchromatic light-harvesting and charge separation. RSC Adv 2018; 8:23854-23874. [PMID: 35540249 PMCID: PMC9081848 DOI: 10.1039/c8ra04052d] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 06/15/2018] [Indexed: 12/14/2022] Open
Abstract
Achieving solar light harvesting followed by efficient charge separation and transport is an essential objective of molecular-based artificial photosynthesis. Architectures that afford strong absorption across the near-UV to near-infrared region, namely panchromatic absorptivity, are critically important given the broad spectral distribution of sunlight. A tetrapyrrole–perylene pentad array was synthesized and investigated as a means to integrate panchromatic light harvesting and intramolecular charge separation. The pentad consists of three moieties: (1) a panchromatically absorbing triad, in which a porphyrin is strongly coupled to two perylene-monoimides via ethyne linkages; (2) a perylene-diimide electron acceptor; and (3) a chlorin hole-trapping unit. Integrating the three components with diphenylethyne linkers generates moderate electronic coupling for intramolecular energy and hole/electron transfer. The construction of the array relies on a stepwise strategy for incorporating modular pigment building blocks. The key building blocks include a trans-A2BC porphyrin, a chlorin, a perylene-monoimide, and a perylene-diimide, each bearing appropriate (halo, ethynyl) synthetic handles for Pd-catalyzed Sonogashira coupling reactions. One target pentad, three tetrads, four triads, and four monomeric benchmark compounds were synthesized from six building blocks (three new, three reported) and 10 new synthetic intermediates. Four of the tetrapyrrole-containing arrays are zinc chelated, and four others are in the free base form. Absorption and fluorescence spectra and fluorescence quantum yields were also measured. Collectively, investigations of the arrays reveal insights into principles for the design of novel reaction centers integrated with a panchromatic antenna for artificial photosynthetic studies. Twelve arrays containing porphyrin, chlorin, and/or perylene-imide units were synthesized to investigate panchromatic absorption integrated with charge separation.![]()
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Mandal AK, Diers JR, Niedzwiedzki DM, Hu G, Liu R, Alexy EJ, Lindsey JS, Bocian DF, Holten D. Tailoring Panchromatic Absorption and Excited-State Dynamics of Tetrapyrrole–Chromophore (Bodipy, Rylene) Arrays—Interplay of Orbital Mixing and Configuration Interaction. J Am Chem Soc 2017; 139:17547-17564. [DOI: 10.1021/jacs.7b09548] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Jiao J, Yu M, Holten D, Lindsey JS, Bocian DF. Characterization of Hydroporphyrins Covalently Attached to Si(100). J PORPHYR PHTHALOCYA 2017. [DOI: 10.1142/s1088424617500547] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Attachment of synthetic analogs of natural tetrapyrroles to electroactive surfaces enables physicochemical interrogation and may provide material for use in catalysis, diagnostics, and energy conversion. Six synthetic zinc chlorins and one free base bacteriochlorin, tailored analogs of chlorophyll and bacteriochlorophyll, respectively, have been attached to Si(100) via a high-temperature (400°C) baking method. The hydroporphyrins bear diverse functional groups that enable surface attachment (vinyl, acetyl, triisopropylsilylethynyl, pentafluorophenyl, and hydroxymethylphenyl) and a geminal dimethyl group in each reduced ring for stabilization toward adventitious dehydrogenation. The films were examined by cyclic voltammetry, FTIR spectroscopy, X-ray photoelectron spectroscopy, and ellipsometry. Monofunctionalized and difunctionalized hydroporphyrins gave monolayer and multilayer films, respectively, indicating robustness of the hydroporphyrin molecules, but in each case the film was more heterogeneous than observed with comparable porphyrins. The data suggest that some amount of unattached molecules remain intercalated with surface-attached molecules. Additional molecular designs will need to be examined to develop a deep understanding of the structure-activity relationship for formation of homogeneous monolayers and multilayers of synthetic hydroporphyrins.
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Hood D, Niedzwiedzki DM, Zhang R, Zhang Y, Dai J, Miller ES, Bocian DF, Williams PG, Lindsey JS, Holten D. Photophysical Characterization of the Naturally Occurring Dioxobacteriochlorin Tolyporphin A and Synthetic Oxobacteriochlorin Analogues. Photochem Photobiol 2017; 93:1204-1215. [DOI: 10.1111/php.12781] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 04/04/2017] [Indexed: 01/21/2023]
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Faries KM, Dylla NP, Hanson DK, Holten D, Laible PD, Kirmaier C. Manipulating the Energetics and Rates of Electron Transfer in Rhodobacter capsulatus Reaction Centers with Asymmetric Pigment Content. J Phys Chem B 2017; 121:6989-7004. [DOI: 10.1021/acs.jpcb.7b01389] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Niedzwiedzki DM, Dilbeck PL, Tang Q, Martin EC, Bocian DF, Hunter CN, Holten D. New insights into the photochemistry of carotenoid spheroidenone in light-harvesting complex 2 from the purple bacterium Rhodobacter sphaeroides. PHOTOSYNTHESIS RESEARCH 2017; 131:291-304. [PMID: 27854005 PMCID: PMC5313593 DOI: 10.1007/s11120-016-0322-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Accepted: 10/24/2016] [Indexed: 06/06/2023]
Abstract
Light-harvesting complex 2 (LH2) from the semi-aerobically grown purple phototrophic bacterium Rhodobacter sphaeroides was studied using optical (static and time-resolved) and resonance Raman spectroscopies. This antenna complex comprises bacteriochlorophyll (BChl) a and the carotenoid spheroidenone, a ketolated derivative of spheroidene. The results indicate that the spheroidenone-LH2 complex contains two spectral forms of the carotenoid: (1) a minor, "blue" form with an S2 (11B u+ ) spectral origin band at 522 nm, shifted from the position in organic media simply by the high polarizability of the binding site, and (2) the major, "red" form with the origin band at 562 nm that is associated with a pool of pigments that more strongly interact with protein residues, most likely via hydrogen bonding. Application of targeted modeling of excited-state decay pathways after carotenoid excitation suggests that the high (92%) carotenoid-to-BChl energy transfer efficiency in this LH2 system, relative to LH2 complexes binding carotenoids with comparable double-bond conjugation lengths, derives mainly from resonance energy transfer from spheroidenone S2 (11B u+ ) state to BChl a via the Qx state of the latter, accounting for 60% of the total transfer. The elevated S2 (11B u+ ) → Qx transfer efficiency is apparently associated with substantially decreased energy gap (increased spectral overlap) between the virtual S2 (11B u+ ) → S0 (11A g- ) carotenoid emission and Qx absorption of BChl a. This reduced energetic gap is the ultimate consequence of strong carotenoid-protein interactions, including the inferred hydrogen bonding.
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Liu Y, Allu S, Nagarjuna Reddy M, Hood D, Diers JR, Bocian DF, Holten D, Lindsey JS. Synthesis and photophysical characterization of bacteriochlorins equipped with integral swallowtail substituents. NEW J CHEM 2017. [DOI: 10.1039/c7nj00499k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The two pyrroline units of bacteriochlorins can now bear gem-dialkyl or diaryl groups (L), which project above and below the macrocycle plane, whereas dimethyl groups generally have been accessible previously.
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Liu M, Chen CY, Hood D, Taniguchi M, Diers JR, Bocian DF, Holten D, Lindsey JS. Synthesis, photophysics and electronic structure of oxobacteriochlorins. NEW J CHEM 2017. [DOI: 10.1039/c6nj04135c] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthetic oxobacteriochlorins exhibit strong absorption in the deep-red window flanked by chlorins to the red and bacteriochlorins to the near-infrared.
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Mandal AK, Taniguchi M, Diers JR, Niedzwiedzki DM, Kirmaier C, Lindsey JS, Bocian DF, Holten D. Photophysical Properties and Electronic Structure of Porphyrins Bearing Zero to Four meso-Phenyl Substituents: New Insights into Seemingly Well Understood Tetrapyrroles. J Phys Chem A 2016; 120:9719-9731. [DOI: 10.1021/acs.jpca.6b09483] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Amanpour J, Hu G, Alexy EJ, Mandal AK, Kang HS, Yuen JM, Diers JR, Bocian DF, Lindsey JS, Holten D. Tuning the Electronic Structure and Properties of Perylene-Porphyrin-Perylene Panchromatic Absorbers. J Phys Chem A 2016; 120:7434-50. [PMID: 27636001 DOI: 10.1021/acs.jpca.6b06857] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Light-harvesting architectures that afford strong absorption across the near-ultraviolet to near-infrared region, namely, panchromatic absorptivity, are potentially valuable for capturing the broad spectral distribution of sunlight. One previously reported triad consisting of two perylene monoimides strongly coupled to a free base porphyrin via ethyne linkers (FbT) shows panchromatic absorption together with a porphyrin-like S1 excited state albeit at lower energy than that of a typical monomeric porphyrin. Here, two new porphyrin-bis(perylene) triads have been prepared wherein the porphyrin bears two pentafluorophenyl substituents. The porphyrin is in the free base (FbT-F) or zinc chelate (ZnT-F) forms. The zinc chelate (ZnT) of the original triad bearing nonfluorinated aryl rings also was prepared. The triads were characterized using static and time-resolved optical spectroscopy. The results were analyzed with the aid of molecular-orbital characteristics obtained using density functional theory calculations. Of the four triads, FbT is the most panchromatic in affording the most even distribution of absorption spectral intensity as well as exhibiting the largest wavelength span (380-750 nm). The triads exhibit fluorescence yields (0.35 for FbT-F in toluene) that are substantially greater than for the porphyrin benchmarks (0.049 for FbP-F). The singlet excited-state lifetimes (τS) for the triads in toluene decrease in the order FbT-F (2.7 ns) > FbT (2.0 ns) > ZnT (1.2 ns) ∼ ZnT-F (1.1 ns). The τS values in benzonitrile are FbT (1.3 ns) > FbT-F (1.2 ns) > ZnT-F (0.6 ns) > ZnT (0.2 ns). Thus, the free base triads exhibit relatively long (1.2-2.7 ns) excited-state lifetimes in both polar and nonpolar media. The combined photophysical characteristics indicate that FbT and FbT-F are the best choices for panchromatic light-harvesting systems. Collectively, the findings afford insights into the effects of electronic structure on the panchromatic behavior of ethynyl-linked porphyrin-perylene architectures that can help guide next-generation designs and utilization of these systems.
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Zhang N, Jiang J, Liu M, Taniguchi M, Mandal AK, Evans-Storms RB, Pitner JB, Bocian DF, Holten D, Lindsey JS. Bioconjugatable, PEGylated Hydroporphyrins for Photochemistry and Photomedicine. Narrow-Band, Near-Infrared-Emitting Bacteriochlorins. NEW J CHEM 2016; 40:7750-7767. [PMID: 28133433 DOI: 10.1039/c6nj01155a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Synthetic bacteriochlorins absorb in the near-infrared (NIR) region and are versatile analogues of natural bacteriochlorophylls. The utilization of these chromophores in energy sciences and photomedicine requires the ability to tailor their physicochemical properties, including the incorporation of units to impart water solubility. Herein, we report the synthesis, from two common bacteriochlorin building blocks, of five wavelength-tunable, bioconjugatable and water-soluble bacteriochlorins along with two non-bioconjugatable benchmarks. Each bacteriochlorin bears short polyethylene glycol (PEG) units as the water-solubilizing motif. The PEG groups are located at the 3,5-positions of aryl groups at the pyrrolic β-positions to suppress aggregation in aqueous media. A handle containing a single carboxylic acid is incorporated to allow bioconjugation. The seven water-soluble bacteriochlorins in water display Qy absorption into the NIR range (679-819 nm), sharp emission (21-36 nm full-width-at-half-maximum) and modest fluorescence quantum yield (0.017-0.13). Each bacteriochlorin is neutral (non-ionic) yet soluble in organic (e.g., CH2Cl2, DMF) and aqueous solutions. Water solubility was assessed using absorption spectroscopy by changing the concentration ∼1000-fold (190-690 µM to 0.19-0.69 µM) with a reciprocal change in pathlength (0.1-10 cm). All bacteriochlorins showed excellent solubility in water, except for a bacteriochlorin-imide that gave slight aggregation at higher concentrations. One bacteriochlorin was conjugated to a mouse polyclonal IgG antibody for use in flow cytometry with compensation beads for proof-of-principle. The antibody conjugate of B2-NHS displayed a sharp signal upon ultraviolet laser excitation (355 nm) with NIR emission measured with a 730/45 nm bandpass filter. Overall, the study gives access to a set of water-soluble bacteriochlorins with desirable photophysical properties for use in multiple fields.
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Liu M, Chen CY, Mandal AK, Chandrashaker V, Evans-Storms RB, Pitner JB, Bocian DF, Holten D, Lindsey JS. Bioconjugatable, PEGylated Hydroporphyrins for Photochemistry and Photomedicine. Narrow-Band, Red-Emitting Chlorins. NEW J CHEM 2016; 40:7721-7740. [PMID: 28154477 DOI: 10.1039/c6nj01154c] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Chromophores that absorb and emit in the red spectral region (600-700 nm), are water soluble, and bear a bioconjugatable tether are relatively rare yet would fulfill many applications in photochemistry and photomedicine. Here, three molecular designs have been developed wherein stable synthetic chlorins - analogues of chlorophylls - have been tailored with PEG groups for use in aqueous solution. The designs differ with regard to order of the installation (pre/post-formation of the chlorin macrocycle) and position of the PEG groups. Six PEGylated synthetic chlorins (three free bases, three zinc chelates) have been prepared, of which four are equipped with a bioconjugatable (carboxylic acid) tether. The most effective design for aqueous solubilization entails facial encumbrance where PEG groups project above and below the plane of the hydrophobic disk-like chlorin macrocycle. The chlorins possess strong absorption at ~400 nm (B band) and in the red region (Qy band); regardless of wavelength of excitation, emission occurs in the red region. Excitation in the ~400 nm region thus provides an effective Stokes shift of >200 nm. The four bioconjugatable water-soluble chlorins exhibit Qy absorption/emission in water at 613/614, 636/638, 698/700 and 706/710 nm. The spectral properties are essentially unchanged in DMF and water for the facially encumbered chlorins, which also exhibit narrow Qy absorption and emission bands (full-width-at-half maximum of each <25 nm). The water-solubility was assessed by absorption spectroscopy over the concentration range ~0.4 μM - 0.4 mM. One chlorin was conjugated to a mouse polyclonal IgG antibody for use in flow cytometry with compensation beads for proof-of-principle. The conjugate displayed a sharp signal when excited by a violet laser (405 nm) with emission in the 620-660 nm range. Taken together, the designs described herein augur well for development of a set of spectrally distinct chlorins with relatively sharp bands in the red region.
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Dylla NP, Faries KM, Wyllie RM, Swenson AM, Hanson DK, Holten D, Kirmaier C, Laible PD. Species differences in unlocking B‐side electron transfer in bacterial reaction centers. FEBS Lett 2016; 590:2515-26. [DOI: 10.1002/1873-3468.12264] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 06/13/2016] [Indexed: 11/09/2022]
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Dilbeck PL, Tang Q, Mothersole DJ, Martin EC, Hunter CN, Bocian DF, Holten D, Niedzwiedzki DM. Quenching Capabilities of Long-Chain Carotenoids in Light-Harvesting-2 Complexes from Rhodobacter sphaeroides with an Engineered Carotenoid Synthesis Pathway. J Phys Chem B 2016; 120:5429-43. [PMID: 27285777 PMCID: PMC4921951 DOI: 10.1021/acs.jpcb.6b03305] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Six light-harvesting-2 complexes
(LH2) from genetically modified
strains of the purple photosynthetic bacterium Rhodobacter
(Rb.) sphaeroides were studied using static and ultrafast
optical methods and resonance Raman spectroscopy. These strains were
engineered to incorporate carotenoids for which the number of conjugated
groups (N = NC=C + NC=O) varies from 9 to 15.
The Rb. sphaeroides strains incorporate their native
carotenoids spheroidene (N = 10) and spheroidenone
(N = 11), as well as longer-chain analogues including
spirilloxanthin (N = 13) and diketospirilloxantion
(N = 15) normally found in Rhodospirillum
rubrum. Measurements of the properties of the carotenoid
first singlet excited state (S1) in antennas from the Rb. sphaeroides set show that carotenoid-bacteriochlorophyll a (BChl a) interactions are similar to
those in LH2 complexes from various other bacterial species and thus
are not significantly impacted by differences in polypeptide composition.
Instead, variations in carotenoid-to-BChl a energy
transfer are primarily regulated by the N-determined
energy of the carotenoid S1 excited state, which for long-chain
(N ≥ 13) carotenoids is not involved in energy
transfer. Furthermore, the role of the long-chain carotenoids switches
from a light-harvesting supporter (via energy transfer to BChl a) to a quencher of the BChl a S1 excited state B850*. This quenching is manifested as a substantial
(∼2-fold) reduction of the B850* lifetime and the B850* fluorescence
quantum yield for LH2 housing the longest carotenoids.
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Faries KM, Kressel LL, Dylla NP, Wander MJ, Hanson DK, Holten D, Laible PD, Kirmaier C. Optimizing multi-step B-side charge separation in photosynthetic reaction centers from Rhodobacter capsulatus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:150-159. [DOI: 10.1016/j.bbabio.2015.11.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 11/20/2015] [Accepted: 11/30/2015] [Indexed: 11/16/2022]
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Kang HS, Esemoto NN, Diers JR, Niedzwiedzki DM, Greco JA, Akhigbe J, Yu Z, Pancholi C, Bhagavathy GV, Nguyen JK, Kirmaier C, Birge RR, Ptaszek M, Holten D, Bocian DF. Effects of Strong Electronic Coupling in Chlorin and Bacteriochlorin Dyads. J Phys Chem A 2016; 120:379-95. [PMID: 26765839 DOI: 10.1021/acs.jpca.5b10686] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Achieving tunable, intense near-infrared absorption in molecular architectures with properties suitable for solar light harvesting and biomedical studies is of fundamental interest. Herein, we report the photophysical, redox, and molecular-orbital characteristics of nine hydroporphyrin dyads and associated benchmark monomers that have been designed and synthesized to attain enhanced light harvesting. Each dyad contains two identical hydroporphyrins (chlorin or bacteriochlorin) connected by a linker (ethynyl or butadiynyl) at the macrocycle β-pyrrole (3- or 13-) or meso (15-) positions. The strong electronic communication between constituent chromophores is indicated by the doubling of prominent absorption features, split redox waves, and paired linear combinations of frontier molecular orbitals. Relative to the benchmarks, the chlorin dyads in toluene show substantial bathochromic shifts of the long-wavelength absorption band (17-31 nm), modestly reduced singlet excited-state lifetimes (τS = 3.6-6.2 ns vs 8.8-12.3 ns), and increased fluorescence quantum yields (Φf = 0.37-0.57 vs 0.34-0.39). The bacteriochlorin dyads in toluene show significant bathochromic shifts (25-57 nm) and modestly reduced τS (1.6-3.4 ns vs 3.5-5.3 ns) and Φf (0.09-0.19 vs 0.17-0.21) values. The τS and Φf values for the bacteriochlorin dyads are reduced substantially (up to ∼20-fold) in benzonitrile. The quenching is due primarily to the increased S1 → S0 internal conversion that is likely induced by increased contribution of charge-resonance configurations to the S1 excited state in the polar medium. The fundamental insights gained into the physicochemical properties of the strongly coupled hydroporphyrin dyads may aid their utilization in solar-energy conversion and photomedicine.
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Hu G, Liu R, Alexy EJ, Mandal AK, Bocian DF, Holten D, Lindsey JS. Panchromatic chromophore–tetrapyrrole light-harvesting arrays constructed from Bodipy, perylene, terrylene, porphyrin, chlorin, and bacteriochlorin building blocks. NEW J CHEM 2016. [DOI: 10.1039/c6nj01782g] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Five new chromophore–tetrapyrrole arrays bearing an ethynyl linker have been synthesized to explore the effects of chromophore nature and tetrapyrrole attachment site on panchromatic spectral properties.
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Zhang S, Kim HJ, Tang Q, Yang E, Bocian DF, Holten D, Lindsey JS. Synthesis and photophysical characteristics of 2,3,12,13-tetraalkylbacteriochlorins. NEW J CHEM 2016. [DOI: 10.1039/c6nj00517a] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Tetraalkylbacteriochlorins, available upon acid-mediated self-condensation of α-ester stabilized dihydrodipyrrin-carboxaldehydes, provide valuable models of the naturally occurring bacteriochlorophylls.
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Mandal AK, Sahin T, Liu M, Lindsey JS, Bocian DF, Holten D. Photophysical comparisons of PEGylated porphyrins, chlorins and bacteriochlorins in water. NEW J CHEM 2016. [DOI: 10.1039/c6nj02091g] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Synthesis of a bioconjugatable water-soluble (PEGylated) trans-AB-porphyrin enables photophysical comparisons (τS, kf, kic, kisc, Φf, Φic, Φisc) with analogous chlorins and bacteriochlorins in DMF and water.
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Yang E, Zhang N, Krayer M, Taniguchi M, Diers JR, Kirmaier C, Lindsey JS, Bocian DF, Holten D. Integration of Cyanine, Merocyanine and Styryl Dye Motifs with Synthetic Bacteriochlorins. Photochem Photobiol 2015; 92:111-25. [PMID: 26505265 DOI: 10.1111/php.12547] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 10/02/2015] [Indexed: 12/19/2022]
Abstract
Understanding the effects of substituents on spectral properties is essential for the rational design of tailored bacteriochlorins for light-harvesting and other applications. Toward this goal, three new bacteriochlorins containing previously unexplored conjugating substituents have been prepared and characterized. The conjugating substituents include two positively charged species, 2-(N-ethyl 2-quinolinium)vinyl- (B-1) and 2-(N-ethyl 4-pyridinium)vinyl- (B-2), and a neutral group, acroleinyl- (B-3); the charged species resemble cyanine (or styryl) dye motifs whereas the neutral unit resembles a merocyanine dye motif. The three bacteriochlorins are examined by static and time-resolved absorption and emission spectroscopy and density functional theoretical calculations. B-1 and B-2 have Qy absorption bathochromically shifted well into the NIR region (822 and 852 nm), farther than B-3 (793 nm) and other 3,13-disubstituted bacteriochlorins studied previously. B-1 and B-2 have broad Qy absorption and fluorescence features with large peak separation (Stokes shift), low fluorescence yields, and shortened S1 (Qy ) excited-state lifetimes (~700 ps and ~100 ps). More typical spectra and S1 lifetime (~2.3 ns) are found for B-3. The combined photophysical and molecular-orbital characteristics suggest the altered spectra and enhanced nonradiative S1 decay of B-1 and B-2 derive from excited-state configurations in which electron density is shifted between the macrocycle and the substituents.
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Sahin T, Harris MA, Vairaprakash P, Niedzwiedzki DM, Subramanian V, Shreve AP, Bocian DF, Holten D, Lindsey JS. Self-Assembled Light-Harvesting System from Chromophores in Lipid Vesicles. J Phys Chem B 2015; 119:10231-43. [PMID: 26230425 DOI: 10.1021/acs.jpcb.5b04841] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lipid vesicles are used as the organizational structure of self-assembled light-harvesting systems. Following analysis of 17 chromophores, six were selected for inclusion in vesicle-based antennas. The complementary absorption features of the chromophores span the near-ultraviolet, visible, and near-infrared region. Although the overall concentration of the pigments is low (~1 μM for quantitative spectroscopic studies) in a cuvette, the lipid-vesicle system affords high concentration (≥10 mM) in the bilayer for efficient energy flow from donor to acceptor. Energy transfer was characterized in 13 representative binary mixtures using static techniques (fluorescence-excitation versus absorptance spectra, quenching of donor fluorescence, modeling emission spectra of a mixture versus components) and time-resolved spectroscopy (fluorescence, ultrafast absorption). Binary donor-acceptor systems that employ a boron-dipyrrin donor (S0 ↔ S1 absorption/emission in the blue-green) and a chlorin or bacteriochlorin acceptor (S0 ↔ S1 absorption/emission in the red or near-infrared) have an average excitation-energy-transfer efficiency (ΦEET) of ~50%. Binary systems with a chlorin donor and a chlorin or bacteriochlorin acceptor have ΦEET ∼ 85%. The differences in ΦEET generally track the donor-fluorescence/acceptor-absorption spectral overlap within a dipole-dipole coupling (Förster) mechanism. Substantial deviation from single-exponential decay of the excited donor (due to the dispersion of donor-acceptor distances) is expected and observed. The time profiles and resulting ΦEET are modeled on the basis of (Förster) energy transfer between chromophores relatively densely packed in a two-dimensional compartment. Initial studies of two ternary and one quaternary combination of chromophores show the enhanced spectral coverage and energy-transfer efficacy expected on the basis of the binary systems. Collectively, this approach may provide one of the simplest designs for self-assembled light-harvesting systems that afford broad solar collection and efficient energy transfer.
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Niedzwiedzki DM, Dilbeck PL, Tang Q, Mothersole DJ, Martin EC, Bocian DF, Holten D, Hunter CN. Functional characteristics of spirilloxanthin and keto-bearing Analogues in light-harvesting LH2 complexes from Rhodobacter sphaeroides with a genetically modified carotenoid synthesis pathway. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1847:640-55. [PMID: 25871644 DOI: 10.1016/j.bbabio.2015.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 04/01/2015] [Accepted: 04/03/2015] [Indexed: 11/24/2022]
Abstract
Light-harvesting 2 (LH2) complexes from a genetically modified strain of the purple photosynthetic bacterium Rhodobacter (Rba.) sphaeroides were studied using static and ultrafast optical methods and resonance Raman spectroscopy. Carotenoid synthesis in the Rba. sphaeroides strain was engineered to redirect carotenoid production away from spheroidene into the spirilloxanthin synthesis pathway. The strain assembles LH2 antennas with substantial amounts of spirilloxanthin (total double-bond conjugation length N=13) if grown anaerobically and of keto-bearing long-chain analogs [2-ketoanhydrorhodovibrin (N=13), 2-ketospirilloxanthin (N=14) and 2,2'-diketospirilloxanthin (N=15)] if grown semi-aerobically (with ratios that depend on growth conditions). We present the photophysical, electronic, and vibrational properties of these carotenoids, both isolated in organic media and assembled within LH2 complexes. Measurements of excited-state energy transfer to the array of excitonically coupled bacteriochlorophyll a molecules (B850) show that the mean lifetime of the first singlet excited state (S1) of the long-chain (N≥13) carotenoids does not change appreciably between organic media and the protein environment. In each case, the S1 state appears to lie lower in energy than that of B850. The energy-transfer yield is ~0.4 in LH2 (from the strain grown aerobically or semi-aerobically), which is less than half that achieved for LH2 that contains short-chain (N≤11) analogues. Collectively, the results suggest that the S1 excited state of the long-chain (N≥13) carotenoids participates little if at all in carotenoid-to-BChl a energy transfer, which occurs predominantly via the carotenoid S2 excited state in these antennas.
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Vairaprakash P, Yang E, Sahin T, Taniguchi M, Krayer M, Diers JR, Wang A, Niedzwiedzki DM, Kirmaier C, Lindsey JS, Bocian DF, Holten D. Extending the Short and Long Wavelength Limits of Bacteriochlorin Near-Infrared Absorption via Dioxo- and Bisimide-Functionalization. J Phys Chem B 2015; 119:4382-95. [DOI: 10.1021/jp512818g] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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