skip to main content


Title: Structure, Properties, and Reactivity of Porphyrins on Surfaces and Nanostructures with Periodic DFT Calculations
Porphyrins are fascinating molecules with applications spanning various scientific fields. In this review we present the use of periodic density functional theory (PDFT) calculations to study the structure, electronic properties, and reactivity of porphyrins on ordered two dimensional surfaces and in the formation of nanostructures. The focus of the review is to describe the application of PDFT calculations for bridging the gaps in experimental studies on porphyrin nanostructures and self-assembly on 2D surfaces. A survey of different DFT functionals used to study the porphyrin-based system as well as their advantages and disadvantages in studying these systems is presented.  more » « less
Award ID(s):
1800070
NSF-PAR ID:
10162707
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Applied Sciences
Volume:
10
Issue:
3
ISSN:
2076-3417
Page Range / eLocation ID:
740
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. With potential applications in materials and especially in light-responsive biomedicine that targets cancer tissue selectively, much research has focused on developing covalent conjugation techniques to tether porphyrinoid units to various biomacromolecules. This review details the key synthetic approaches that have been employed in the recent decades to conjugate porphyrinoids with oligonucleotides and peptides/proteins. In addition, we provide succinct discussions on the subsequent applications of such hybrid systems and also give a brief overview of the rapidly progressing field of porphyrin-antibody conjugates. Since nucleic acid and peptide systems vary in structure, connectivity, functional group availability and placement, as well as stability and solubility, tailored synthetic approaches are needed for conjugating to each of these biomacromolecule types. In terms of tethering to ONs, porphyrins are typically attached by employing bioorthogonal chemistry (e.g., using phosphoramidites) that drive solid-phase ON synthesis or by conducting post-synthesis modifications and subsequent reactions (such as amide couplings, hydrazide-carbonyl reactions, and click chemistry). In contrast, peptides and proteins are typically conjugated to porphyrinoids using their native functional groups, especially the thiol and amine side chains. However, bioorthogonal reactions (e.g., Staudinger ligations, and copper or strain promoted alkyne-azide cycloadditions) that utilize de novo introduced functional groups onto peptides/proteins have seen vigorous development, especially for site-specific peptide-porphyrin tethering. While the ON-porphyrin conjugates have largely been explored for programmed nanostructure self-assembly and artificial light-harvesting applications, there are some reports of ON-porphyrin systems targeting clinically translational applications (e.g., antimicrobial biomaterials and site-specific nucleic acid cleavage). Conjugates of porphyrins with proteinaceous moieties, on the other hand, have been predominantly used for therapeutic and diagnostic applications (especially in photodynamic therapy, photodynamic antimicrobial chemotherapy, and photothermal therapy). The advancement of the field of porphyrinoid-bioconjugation chemistry from basic academic research to more clinically targeted applications require continuous fine-tuning in terms of synthetic strategies and hence there will continue to be much exciting work on porphyrinoid-biomacromolecule conjugation. 
    more » « less
  2. Abstract

    A series ofmeso‐substituted with aromatic (=tolyl, pyrenyl, fluorenyl, naphthyl, and triphenylamine) substituents, platinum (Pt), and palladium (Pd) porphyrins have been synthesized and characterized by spectroscopic and single‐crystal X‐ray diffraction studies to probe structure‐reactivity aspects on the electrochemical redox potentials, and phosphorescence quantum yields and lifetimes. In the X‐ray structures, the aromaticmeso‐substituents were rotated to some extent from the planarity of the porphyrin ring to minimize steric hindrance. Both Pt and Pd porphyrins revealed higher electrochemical redox gaps as compared to their free‐base porphyrin analogs as a result of the harder oxidation and reduction processes. The ability of both Pt and Pd porphyrins to generate singlet oxygen was probed by monitoring the photoluminescence of1O2at 1270 nm. Higher quantum yields for both triplet sensitizers compared to their free‐base analogs were witnessed. Singlet oxygen quantum yields close to unity were possible to achieve in the case of Pt and Pd porphyrins bearing triphenylamine substituents at themeso‐position. The present study brings out the importance of differentmeso‐substituents on the triplet porphyrin sensitizers in governing singlet oxygen quantum yields; a key property of photosensitizers needed for photodynamic therapy, chemical synthesis, and other pertinent applications.

     
    more » « less
  3. Abstract

    A novel class of β‐functionalized push–pull zincopp‐dibenzoporphyrins were designed, synthesized, and utilized as sensitizers for dye‐sensitized solar cells. Spectral, electrochemical, and computational studies were systematically performed to evaluate their spectral coverage, redox behavior, and electronic structures. These porphyrins displayed much broader spectral coverage and more facile oxidation upon extension of the π conjugation. Free‐energy calculations and femtosecond transient absorption studies (charge injection rate in the range of 1011 s−1) suggested efficient charge injection from the excited singlet state of the porphyrin to the conduction band of TiO2. The power conversion efficiency (η) ofYH3bearing acrylic acid linkers (η=5.9 %) was close to that of the best ruthenium dye N719 (η=7.4 %) under similar conditions. The superior photovoltaic performance ofYH3was attributed to its higher light‐harvesting ability and more favorable electron injection and collection, as supported by electrochemical impedance spectral studies. This work demonstrates the exceptional potential of benzoporphyrins as sensitizers for dye‐sensitized solar cells.

     
    more » « less
  4. Abstract

    The fusion of tetrapyrroles with aromatic heterocycles constitutes a useful tool for manipulating their opto‐electronic properties. In this work, the synthesis of naphthodithiophene‐fused porphyrins was achieved through a Heck reaction‐based cascade of steps followed by the Scholl reaction. The naphthodithiophene‐fused porphyrins display a unique set of optical and electronic properties. Fusion of the naphtho[2,1‐b:3,4‐b’]dithiophene to porphyrin (F2VTP) leads to a ~20% increase in the fluorescence lifetime, which is accompanied, unexpectedly, by a more than two‐fold drop in the emission quantum yield (ϕ=0.018). In contrast, fusion of the isomeric naphtho[1,2‐b:4,3‐b’]dithiophene to porphyrin (F3VPT)results in a ~1.5‐fold increase in the fluorescence quantum yield (ϕ=0.13) with a concomitant ~30 % increase in the fluorescence lifetime. This behavior suggests that fusion of the porphyrin with the naphthodithiopheno‐system mainly affects the radiative rate constant in the Q‐state deactivation pathway, where the effects of the isomeric naphtho[2,1‐b:3,4‐b’]dithiophene‐ versus naphtho[1,2‐b:4,3‐b’]dithiophene‐fusion are essentially the opposite. Interestingly, nucleus‐independent chemical shifts analysis revealed a considerable difference between the aromaticities of these two isomeric systems. Our results demonstrate that subtle structural differences in the fused components of the porphyrin can be reflected in rather significant differences between the photophysical properties of the resulting systems.

     
    more » « less
  5. null (Ed.)
    Neo-confused porphyrins (neo-CPs), porphyrin isomers with a 1,3-connected pyrrolic subunit, are aromatic structures with a CNNN coordination core. Previously, examples of neo-CPs with fused benzo units or electron-withdrawing ester substituents have been described. In this paper, two new examples of neo-CPs are reported that lack a fused aromatic unit or an ester moiety, but instead have a bromo or phenyl substituent on the neo-confused ring. Acid-catalyzed condensation of suitably substituted 1,2′-dipyrrylmethane dialdehydes with a 2,2′-dipyrrylmethane, followed by oxidation with aqueous ferric chloride solutions, afforded the neo-CPs in 40–45% yield. These porphyrin analogues had slightly reduced diatropic ring currents and slowly decomposed in solution. The related palladium( ii ) and nickel( ii ) complexes proved to be very unstable, even though the diatropicity of the macrocycle was enhanced. This study shows that stabilizing substituents are necessary for investigations into this class of porphyrinoids. Attempts to prepare imidazole versions of neo-CPs were unsuccessful. 
    more » « less