Subscriber access provided by University of Sussex Library
Article
Structure Based Modulation of Electron Dynamics in meso-(4Pyridyl)-BODIPYs: A Computational and Synthetic Approach Daniel J. LaMaster, Nichole E. M. Kaufman, Adam S. Bruner, and M. Graça Henriques Vicente J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.8b05153 • Publication Date (Web): 18 Jul 2018 Downloaded from http://pubs.acs.org on July 24, 2018
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
The Journal of Physical Chemistry
1
Structure Based Modulation of Electron Dynamics
2
in meso-(4-Pyridyl)-BODIPYs: A Computational
3
and Synthetic Approach
4
Daniel J. LaMaster,* Nichole E. M. Kaufman, Adam S. Bruner, and M. Graça H. Vicente*
5
Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
6 7 8 9 10
11
Abstract
12
The effects of structural modification on the electronic structure and electron dynamics of
13
cationic meso-(4-pyridyl)-BODIPYs were investigated. A library of 2,6-difunctionalized meso-
14
(4-pyridyl)-BODIPYs bearing various electron-withdrawing substituents was designed and DFT
15
calculations were used to model the redox properties, while TDDFT was used to determine the
16
effects of functionalization on the excited states. Structural modification was able to restructure
17
the low lying molecular orbitals to effectively inhibit d-PeT. A new meso-(4-pyridyl) BODIPY
18
bearing 2,6-dichloro groups was synthesized and shown to exhibit enhanced charge
19
recombination fluorescence. The fluorescence enhancement was determined to be the result of
20
functionalization modulating the kinetics of the excited state dynamics.
ACS Paragon Plus Environment
The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
1
Introduction
2
Over the past 30 years, there has been a considerable amount of research focused on
3
exploring the chemistry, properties, versatility, and applications of BODIPY dyes that range
4
from tunable laser dyes to probes for biological fluorescence imaging.1-9 One aspect that has
5
been under explored is the development of low molecular weight water-soluble BODIPY
6
derivatives. The first report of a small water-soluble BODIPY was by Worries et al. in 1985
7
which used sulfonate groups to solubilize the fluorophore,10 but by 2007 only a handful of water-
8
soluble BODIPYs had been reported.6
9
solubilization of BODIPY derivatives consists on the introduction of water-solubilizing groups,
10
particularly at the boron center, including: polyethylene glycols,9,11-18 hydroxyls and ethers,19-21
11
amines,19 sulfonamides,21 carboxylates,9,11,17,21-23 sulfonates,9,23-30 phosphonates,9-11 quaternary
12
ammonium salts,8,9,24,28,31,32 carbohydrates,33-35 and peptides.36,37 Most of these groups increase
13
the size of the dye, decrease its stability,38,39 or utilize negative charges which tend to decrease
14
the cell membrane permeability. On the other hand cationic dyes such as rhodamine7 and
15
(poly)cationic porphyrins40 are able to electrostatically interact with the negative charges present
16
on cell membranes, increasing their permeability. Therefore, the investigation of small, cationic,
17
and electron-deficient BODIPYs such as meso-pyridylBODIPYs is of interest, particularly the
18
1,3,5,7-tetramethyl-8-(4-pyridyl)-BODIPY which has C2 symmetry and is readily available from
19
the condensation of 2,4-dimethylpyrrole with 4-pyridylcarboxyaldehyde, followed by oxidation
20
and boron complexation.
21
absorption spectroscopy found that following BODIPY excitation, the dye undergoes donor-
22
photoinduced electron transfer (d-PeT) to a charge transfer state, which is quenched by
23
subsequent intersystem crossing (ISC),41 and the fluorescence quantum yield drops from 0.30 to
Since then, the main strategy used for water-
Previous studies on meso-(4-pyridyl)-BODIPY using transient
ACS Paragon Plus Environment
Page 2 of 26
Page 3 of 26 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
The Journal of Physical Chemistry
1
