The energy of the lowest-lying triplet state (T1) relative to the ground and first-excited singlet states (S0, S1) plays a critical role in optical multiexcitonic processes of organic chromophores. Focusing on triplet–triplet annihilation (TTA) upconversion, the S0 to T1 energy gap, known as the triplet energy, is difficult to measure experimentally for most molecules of interest. Ab initio predictions can provide a useful alternative, however low-scaling electronic structure methods such as the Kohn–Sham and time-dependent variants of Density Functional Theory (DFT) rely heavily on the fraction of exact exchange chosen for a given functional, and tend to be unreliable when strong electronic correlation is present. Here, we use auxiliary-field quantum Monte Carlo (AFQMC), a scalable electronic structure method capable of accurately describing even strongly correlated molecules, to predict the triplet energies for a series of candidate annihilators for TTA upconversion, including 9,10 substituted anthracenes and substituted benzothiadiazole (BTD) and benzoselenodiazole (BSeD) compounds. We compare our results to predictions from a number of commonly used DFT functionals, as well as DLPNO-CCSD(T 0 ), a localized approximation to coupled cluster with singles, doubles, and perturbative triples. Together with S1 estimates from absorption/emission spectra, which are well-reproduced by TD-DFT calculations employing the range-correctedmore »
Quinoline-annulated porphyrin platinum complexes as NIR emitters
The platinum(II) complexes of known quinoline-annulated porphyrins were prepared and spectroscopically characterized. Their optical properties (UV-vis absorption and phosphorescence spectra and phosphorescence lifetimes) were recorded and contrasted against their 2,3-dioxoporphyrin precursor platinum(II) complex. The absorbance and emission spectra (in EtOH glass at 77 K) of the quinoline-annulated porphyrins fall within the NIR optical window of tissue, ranging, depending on the derivative, between [Formula: see text]950 and 1200 nm. The much red-shifted optical spectra, when compared to their non-quinoline-annulated precursors, are attributed to the [Formula: see text]-extension and conformational non-planarity that the annulation causes. The emission yields of the mono-quinoline-annulated derivatives are too low and their lifetimes too short to be practical emitters, but the bis-annulated derivative possesses a practical lifetime and emission yield, suggesting its further exploration, particularly since the methodology toward the solubilization of the quinoline-annulated porphyrins in biological media through derivatization is known.
- Award ID(s):
- 1800361
- Publication Date:
- NSF-PAR ID:
- 10149028
- Journal Name:
- Journal of Porphyrins and Phthalocyanines
- Volume:
- 24
- Issue:
- 01n03
- Page Range or eLocation-ID:
- 386 to 393
- ISSN:
- 1088-4246
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Four groups of rare-earth complexes, comprising 11 new compounds, with fluorinated O-donor ligands ([K(THF)6][Ln(OC4F9)4(THF)2] (1-Ln; Ln = Ce, Nd), [K](THF)x[Ln(OC4F9)4(THF)y] (2-Ln; Ln = Eu, Gd, Dy), [K(THF)2][Ln(pinF)2(THF)3] (3-Ln; Ln = Ce, Nd), and [K(THF)2][Ln(pinF)2(THF)2] (4-Ln; Ln = Eu, Gd, Dy, Y) have been synthesized and characterized. Single-crystal X-ray diffraction data were collected for all compounds except 2-Ln. Species 1-Ln, 3-Ln, and 4-Ln are uncommon examples of six-coordinate (Eu, Gd, Dy, and Y) and seven-coordinate (Ce and Nd) LnIII centers in all-O-donor environments. Species 1-Ln, 2-Ln, 3-Ln, and 4-Ln are all luminescent (except where Ln = Gd and Y), with the solid-state emission of 1-Ce being exceptionally blue-shifted for a Ce complex. The emission spectra of the six Nd, Eu, and Dy complexes do not show large differences based on the ligand and are generally consistent with the well-known free-ion spectra. Time-dependent density functional theory results show that 1-Ce and 3-Ce undergo allowed 5f → 4d excitations, consistent with luminescence lifetime measurements in the nanosecond range. Eu-containing 2-Eu and 4-Eu, however, were found to have luminescence lifetimes in the millisecond range, indicating phosphorescence rather than fluorescence. The performance of a pair of multireference models for prediction of the Ln = Nd,more »
-
Novel tetraaryl-(pyridinium-4-yl)-tetrabenzoporphyrins have been successfully synthesized via a Heck-based sequence reaction. These tetrabenzoporphyrins were substituted with eight pyridyl groups at the fused benzene rings. Methylation of the pyridyl groups with methyl iodide afforded highly water soluble tetrabenzoporphyrins carrying eight ionic groups. The extended [Formula: see text]-conjugation broadened and red-shifted the absorption band of these porphyrins to 650–750 nm. These cationic tetrabenzoporphyrins showed non-toxicity in the dark up to 100 uM. High phototoxicity with IC[Formula: see text] values lower than 18 [Formula: see text]M were obtained for these tetrabenzoporphyrins.
-
Dyads containing two near-infrared absorbing and emitting bacteriochlorins with distinct spectral properties have been prepared and characterized by absorption, emission, and transient-absorption spectroscopies. The dyads exhibit ultrafast ([Formula: see text]3 ps) energy transfer from the bacteriochlorin with the higher-energy S 1 state to the bacteriochlorin emitting at the longer wavelength. The dyads exhibit strong fluorescence and relatively long excited state lifetimes ([Formula: see text]4 ns) in both non-polar and polar solvents, which indicates negligible photoinduced electron transfer between the two bacteriochlorins in the dyads. These dyads are thus attractive for the development of light-harvesting arrays and fluorophores for in vivo bioimaging.
-
The strong spin–orbit coupling (SOC) in lead halide perovskites, when inversion symmetry is lifted, has provided opportunities for investigating the Rashba effect in these systems. Moreover, the strong orbital moment, which, in turn, impacts the spin-pair in singlet and triplet electronic states, plays a significant role in enhancing the optoelectronic properties in the presence of external magnetic fields in lead halide perovskites. Here, we investigate the effect of weak magnetic fields (<1 T) on the photoluminescence (PL) properties of [Formula: see text] nanocrystals with and without Ruddlesden–Popper (RP) faults and single crystals of [Formula: see text]. Along with an enhancement in the PL intensity as a function of an external magnetic field, which is observed in both lead bromide perovskites, the PL emission red-shifts in [Formula: see text] nanocrystals. Density-functional theory calculations of the electronic band-edge in [Formula: see text] show almost no change in the energy gap as a function of the external magnetic field. The experimental results, thus, suggest the role of mixing of the triplet and singlet excitonic states under weak magnetic fields. This is further deduced from an enhancement in PL lifetimes as a function of the field in [Formula: see text]. In [Formula: see text], anmore »
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Publisher's Version of Record
- https://doi.org/10.1142/S1088424619501256
