Conformationally dependent heavy atom effect of chlorine on alkene triplet lifetimes. Experimental and ab initio calculations

Caldwell, Richard A.; Jacobs, Lance D.; Furlani, Thomas R.; Nalley, E. Ann; Laboy, Jorge L.

doi:10.1021/ja00031a013

Cited by 17 publications

(11 citation statements)

References 3 publications

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“…The triplet quantum yield (ϕ T ) of OBPDI in CHCl 3 solution was calculated to be 97 ± 1% by employing the triplet–triplet energy transfer method . An apparent increment in the ϕ T for the OBPDI molecule as compared to the nonbrominated PDI possessing a negligible ϕ T <1% value is due to the efficient ISC rate ensued by the bromine atoms and the core-twist . Upon cumulative addition of bromine atoms on the PDI core, from Br 0 -PDI to Br 8 -PDI, a nonlinear decrease or increase is observed in the ϕ f or ϕ T values, respectively (Figure S6).…”

Section: Resultsmentioning

confidence: 99%

“…21 An apparent increment in the ϕ T for the OBPDI molecule as compared to the nonbrominated PDI possessing a negligible ϕ T <1% value is due to the efficient ISC rate ensued by the bromine atoms and the core-twist. 50 Upon cumulative addition of bromine atoms on the PDI core, from Br 0 -PDI to Br 8 -PDI, a nonlinear decrease or increase is observed in the ϕ f or ϕ T values, respectively (Figure S6). Substitution of four bromine atoms on the ortho position of PDI cause a severe decrease in the fluorescence quantum yield (ϕ f = 21%) 45 when compared to the substitution of the four bromine atoms at the bay position (ϕ f = 69%), possibly due to the effect of the position of substitution in promoting ISC.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Near-Quantitative Triplet State Population via Ultrafast Intersystem Crossing in Perbromoperylenediimide

et al. 2020

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Perylenediimide (PDI) derivatives are essential organic semiconductor materials in a variety of photofunctional devices. By virtue of the large energy gap between the singlet and triplet excited states (ΔE ST = 1.1 eV), augmentation of the triplet state population in monomeric PDI is a challenging task. We report the metal atom-free approach in engendering a near-quantitative triplet yield in perbromoperylenediimide/octabromoperylenediimide (OBPDI), absorbing in the visible region of the electromagnetic spectrum. Perbromination of PDI causes significant out-of-plane distortion (θ = 39°) in the aromatic core of OBPDI as compared to the planar PDI (θ = 0°). A substantial decrease (ΔE 0 red = 0.377 V) in the reduction potential of OBPDI, E 1/2 (OBPDI/OBPDI •− ) = −0.170 V, when compared to the reduction potential, E 1/2 (PDI/PDI •− ) = −0.547 V, of bare PDI makes OBPDI a promising electron acceptor. As a consequence of incorporating eight bromine atoms, the fluorescence quantum yield of a bare PDI chromophore (ϕ f = 97 ± 1%; τ f = 4.54 ns) decreases to a very low value in OBPDI (ϕ f = 3 ± 1%; τ f = 13.78 ps). Femtosecond transient absorption measurements of OBPDI reveal intersystem crossing (ISC) occurring at an ultrafast time scale (τ ISC = 14.20 ps), leading to a near-quantitative triplet population (ϕ T = 97 ± 1%). Theoretical investigations performed to decode the excited state dynamics in OBPDI propose that (i) cumulative addition of eight bromine atoms enhances the magnitude of spin− orbit coupling (SOC) and (ii) twist on the perylene core moderately reduces the energy gap between the singlet−triplet states. Understanding the structural alterations that control the electronic parameters in accessing the triplet excited states of organic chromophores, like PDI, can lead to the design and fabrication of efficient optoelectronic devices and energy storage materials.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Near-Quantitative Triplet State Population via Ultrafast Intersystem Crossing in Perbromoperylenediimide

et al. 2020

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“…Although the molar absorptivity of the studied dyes were within the same range as the commercially available dye, the quantum yield was dramatically increased with the introduction of the electron rich phenyl ring, observing a 23%–47% increase in quantum yield. The chlorine atom at the meso -position of dye IR-780 promotes intersystem crossing due to the heavy atom effect, and allows for the molecule to relax in non-radiative means and decreases the fluorescence [ 31 ].…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Optical Properties of Near-Infrared meso-Phenyl-Substituted Symmetric Heptamethine Cyanine Dyes

2018

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Heptamethine cyanine dyes are a class of near infrared fluorescence (NIRF) probes of great interest in bioanalytical and imaging applications due to their modifiability, allowing them to be tailored for particular applications. Generally, modifications at the meso-position of these dyes are achieved through Suzuki-Miyaura C-C coupling and SRN1 nucleophilic substitution of the chlorine atom at the meso-position of the dye. Herein, a series of 15 meso phenyl-substituted heptamethine cyanines was synthesized utilizing a modified dianil linker. Their optical properties, including molar absorptivity, fluorescence, Stokes shift, and quantum yield were measured. The HSA binding affinities of two representative compounds were measured and compared to that of a series of trimethine cyanines previously synthesized by our lab. The results indicate that the binding of these compounds to HSA is not only dependent on hydrophobicity, but may also be dependent on steric interferences in the binding site and structural dynamics of the NIRF compounds.

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“…It is also found that the rate of decay of the triplet excited state remains independent of degree of bromination in PDI-Br 2−4 . Nonlinear increase in the coretwist angle and Φ T of PDI-Br 0−4 with the increase in number of bromine atoms (Figure S7c, Supporting Information) suggest the dominant role of core-twist 69 in facilitating the triplet generation. Importance of twist angle to facilitate ISC in chromophoric systems was comprehensively established by Caldwell and co-workers.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

“…Importance of twist angle to facilitate ISC in chromophoric systems was comprehensively established by Caldwell and co-workers. 69 Triplet energy level of PDI-Br 4 in toluene (E T = 31 ± 3 kcal/ mol) is experimentally obtained (Figure S8, Supporting Information) through triplet−triplet energy transfer between PDI-Br 4 and an appropriate standard triplet energy donor/ acceptor using Sandros method. 12 Low-lying triplet energy levels (Table S5, Figure S9, Supporting Information) for PDI-Br 0−4 were calculated from TD-DFT method using the B3LYP/ 6-311G+(d, p) 49,50 basis set to understand the driving force for enhanced ISC.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

Access to Triplet Excited State in Core-Twisted Perylenediimide

et al. 2016

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Solvent-free crystal structure of N,N-bis(propylacetyl)-1,6,7,12-tetrabromoperylene-3,4:9,10-bis(dicarboximide), PDI-Br4, obtained by X-ray diffraction reveals the core-twisted perylene motif having π–π stacks at an interplanar separation of 3.7 Å. Slip-stacked arrangement of PDI units in PDI-Br4 arises due to the presence of bulky bromine atoms. Femtosecond pump–probe measurements of monomeric PDI-Br4 in toluene reveal ultrafast intersystem crossing (τISC < 110 fs) when excited at 400 nm. Triplet quantum yield (ΦT) of 19 ± 1% and 105 ± 5% for PDI-Br4 in toluene and vapor-annealed polycrystalline 60 nm thick film respectively are estimated from nanosecond transient absorption measurements. Quantum chemical calculations show that the combined effects of heavy atom and core-twist in PDI-Br4 can activate the intersystem crossing by altering the singlet–triplet energy gap. Enhanced quantum yield accounts for the singlet fission mediated generation of triplet excited state in the PDI-Br4 thin film.

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Conformationally dependent heavy atom effect of chlorine on alkene triplet lifetimes. Experimental and ab initio calculations

Cited by 17 publications

References 3 publications

Near-Quantitative Triplet State Population via Ultrafast Intersystem Crossing in Perbromoperylenediimide

Near-Quantitative Triplet State Population via Ultrafast Intersystem Crossing in Perbromoperylenediimide

Synthesis and Optical Properties of Near-Infrared meso-Phenyl-Substituted Symmetric Heptamethine Cyanine Dyes

Access to Triplet Excited State in Core-Twisted Perylenediimide

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