Luyang Zhao

Density Functional Theory Study on Subtriazaporphyrin Derivatives: Dipolar/Octupolar Contribution to the Second-Order Nonlinear Optical Activity

Density functional theory calculations have been carried out on the subtriazaporphyrin skeletons, an excellent prototype for investigating the dipolar/octupolar contribution to the second-order nonlinear optical (second-order NLO) activity, revealing the size effect and clarifying the nature of the limit when expanding the conjugated system is employed to improve the hyper-Rayleigh scattering response coefficient (β(HRS)). The octupolar and dipolar contributions are theoretically separated, rendering it possible to control the dipolar/octupolar second-order NLO contribution ratio by changing the number and orientation of the peripheral fused benzene moieties. In addition, both the dispersion and solvent effect were also revealed to lead to the enhancement of β(HRS).

Boron–Phenylpyrrin Dyes: Facile Synthesis, Structure, and pH‐Sensitive Properties

Boron-phenylpyrrin dyes: In the presence of BF3⋅OEt2, 4-(diethylamino)salicylaldehyde reacts with substituted pyrroles to give boron-phenylpyrrin dyes, which contain a central boron-containing seven-membered ring. Upon protonation in acidic solution, the complexes, with a large Stokes shift, exhibit a color change and a unique red shift in both the electronic absorption and fluorescence emission spectra (see picture), thus rendering them new analogues of boron-dipyrrin dyes that can be used as pH sensors.

Design of a universal reversible bidirectional current switch based on the fullerene-phthalocyanine supramolecular system.

A novel bidirectional current ON-OFF switch controlled by electron injection and deprivation was proposed on the basis of the density functional theory (DFT) calculation over a fullerene-phthalocyanine supramolecular system PcCoC(60) for the first time. The electron density for PcCoC(60) was revealed to move from fullerene to phthlocyanine only in the oxidized form and from phthlocyanine to fullerene only in the reduced form, reaching the control of electron movement direction by changing the oxidation state of this supramolecular system.

A Special Conjugated Model around sp3 Carbon Atoms: Density Functional Theory Study on the Homoaromatic Electron Delocalization and Applications of Benzo-Fused Tetra(triptycene)porphyrins

The three-unit homoaromatic electron-delocalizing nature of the benzo-fused tetra(triptycene)porphyrins (TTPs) with a three-dimensional conjugated model is clarified using density functional theory studies. Due to the electron delocalization, the unidirectional photon-induced current of this kind of TTP molecular skeleton with a highest efficiency of about 90% in the range between 350 and 500 nm gives them great potential as efficient solar antenna collectors. In addition, their active triptycene cups fused at the central porphyrin core render possible potential application in host-guest chemistry.

The first five-membered-heterocycle-fused subphthalocyanine analogues: chiral tri(benzo[b]thiopheno)subporphyrazines.

Two tri(benzo[b]thiopheno)subporphyrazine regioisomers with C3 and C1 molecular symmetry have been isolated from the cyclotrimerization of benzo[b]thiophene-2,3-dicarbonitrile as the first five-membered-heterocycle-fused subphthalocyanine analogues. Optical resolution of both regioisomers was achieved by using a chiral HPLC technique, affording the first chiral subphthalocyanine analogues.

Substituent effects on the structure–property relationship of unsymmetrical methyloxy and methoxycarbonyl phthalocyanines: DFT and TDDFT theoretical studies

Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were carried out to simulate the molecular and electronic structures together with the electronic absorption spectra of a series of peripheral methyloxy/methoxycarbonyl substituented phthalocyanines M[Pc(β-OMe)(2n)(β-COOMe)(8-2n)] (M=2H, Zn; n=0, 1, 2, 3, and 4). Fragment charge distribution and electrostatic potential analysis indicate that the presence of electron-withdrawing and -donation groups leads to the redistribution of charges and obvious polarization effects to the unsymmetrical phthalocyanine series. Peripheral methyloxy/methoxycarbonyl groups introduced onto phthalocyanine ring were revealed to destroy the degeneracy of LUMOs, resulting in significant Q-band splitting for the unsymmetrical phthalocyanine compounds. In addition, metal-free and zinc phthalocyanine compounds display similar electronic structures and absorptions due to the almost none contribution of the zinc atom or inner hydrogens to the frontier molecular orbitals. The microscopic mechanism of the UV-Vis spectra has been clarified on the basis of multi-band photon-induced electron transference. These theoretical studies would be helpful for the molecular design of novel unsymmetrical phthalocyanines.

The naphthoate-modifying Cu2 +-detective Bodipy sensors with the fluorescent ON-OFF performance unaffected by molecular configuration

Two new boron-dipyrromethenes decorated with 8-hydroxyquinoline-naphthoate moiety, namely 4,4-difluoro-8-(5-(8-hydroxyquinoline-naphthoate))-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (8-HQ-N-DMe-Bodipy) (1) and 4,4-difluoro-8-(5-(8-hydroxyquinoline-naphthoate))-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (8-HQ-N-TMe-Bodipy) (2) have been synthesized. Single crystal X-ray diffraction analysis discloses the very much similar steric arrangement of 8-hydroxyquinoline-naphthoate moiety in these two compounds as revealed by the close torsion angle of C-C-O-C bridge, 174.15 and 171.81° for 1 and 2, respectively, despite the different dihedral angle between quinoline moiety and Bodipy fluorophore for 1 (73.46°) and 2 (82.26°) due to the steric hindrance originated from the C-1/C-7 methyl substituents on Bodipy core for the latter species. Systemic optical studies unravel the red-shifted absorption and fluorescence emission together with slightly lower quantum yield for 1 relative to that of 2, indicating the configuration effect on their spectroscopic properties. However, the binding of Cu2+ with hydroxyquinoline-naphthoate receptor in both 1 and 2 leads to similar fluorescent quenching characteristic due to the photo-induced electron transfer process on the basis of density functional theory calculations, suggesting their high sensitively fluorescent ON-OFF sensing potential to Cu2+ almost unaffected by molecular configuration.

Electronic structures, spectroscopic properties, and reaction activities of porphyrins with alkali metal ions: density functional theory approach to the central metal effects

Density functional theory (DFT) calculation method was employed to investigate a series of nine alkali metal porphyrins (alk-Pors), namely HLiPor, HNaPor, HKPor, Li2Por, LiNaPor, LiKPor, Na2Por, NaKPor, and K2Por. These molecules show different configurations depending on different metal ions which locate over the central hole of the porphyrin ligand. Alk-Pors with larger-radius metal ion have smaller binding energy and thus is more difficult to keep stable. Further detailed molecular stability analysis was carried out by noncovalent interaction and electrostatic interaction via RDG and NBO charge distribution. UV-vis spectra of these nine compounds also show different spectral shapes depending on the central metals, and the dominant state transitions with high degeneracy are revealed to be influenced by high molecular symmetric order. Finally their difference in reactivity due to the electronegativity of central metals and the nature of porphyrin rings are predicted by electrostatic potential and Fukui functions.

Unprecedented phthalocyanine–porphyrin-fused oligomers with induced chirality nature

Optically active binaphthyl units have been introduced onto the periphery of the phthalocyanine chromophores in phthalocyanine–porphyrin-fused oligomers, resulting in the first (R)- and (S)-enantiomers of Pc–Por-fused dimer 1 and trimer 2 with induced chirality nature. This represents the largest chiral tetrapyrrole-based conjugated system, to the best of our knowledge. Electronic absorption, MCD, and CD spectroscopic results in combination with theoretical calculations disclose the effective transfer of the chiral information from the binaphthyl groups to both the central tetrapyrrole-fused chromophores, indicating the effective delocalization of the π-electron density over the fused systems due to the effective electronic communication between/among the tetrapyrrole chromophores.

Ratiometric Fluorescent Detection of Pb2+ by FRET-Based Phthalocyanine-Porphyrin Dyads

Sensitive and selective detection of Pb2+ is a very worthwhile endeavor in terms of both human health and environmental protection, as the heavy metal is fairly ubiquitous and highly toxic. In this study, we designed phthalocyanine-porphyrin (Pc-Por) heterodyads, namely, H2Pc-α-ZnPor (1) and H2Pc-β-ZnPor (2), by connecting a zinc(II) porphyrin moiety to the nonperipheral (α) or peripheral (β) position of a metal-free phthalocyanine moiety. Upon excitation at the porphyrin Soret region (420 nm), both of the dyads exhibited not only a porphyrin emission (605 nm) but also a phthalocyanine emission (ca. 700 nm), indicating the occurrence of intramolecular fluorescence resonance energy transfer (FRET) processes from the porphyrin donor to the phthalocyanine acceptor. The dyads can selectively bind Pb2+ in the phthalocyanine core leading to a red shift of the phthalocyanine absorption and thus a decrease of spectral overlap between the porphyrin emission and phthalocyanine absorption, which in turn suppresses the intramolecular FRET. In addition, the binding of Pb2+ can highly quench the emission of phthalocyanine by heavy-metal ion effects. The synergistic coupled functions endow the dyads with remarkable ratiometric fluorescent responses at two distinct wavelengths (F605/F703 for 1 and F605/F700 for 2). The emission intensity ratio increased as a linear function to the concentration of Pb2+ in the range of 0-4.0 μM, whereas the detection limits were determined to be 3.4 × 10-9 and 2.2 × 10-8 M for 1 and 2, respectively. Furthermore, by comparative study of 1 and 2, the effects of distance and relative orientation between Pc and ZnPor fluorophores on the FRET efficiency and sensing performance were highlighted, which is helpful for further optimizing such FRET systems.