DOI: 10.1002/cphc.201600178
Articles
Theoretical and Experimental Study on Boron
b-Diketonate Complexes with Intense Two-Photon-Induced
Fluorescence in Solution and in the Solid State
Pierre-Henri Lanoꢀ,[a] Bastien Mettra,[a] Yuan Yuan Liao,[a] Nathalie Calin,[a] Anthony D’Alꢁo,*[b]
Tomotaka Namikawa,[c] Kenji Kamada,[c] Frꢁderic Fages,[b] Cyrille Monnereau,*[a] and
Chantal Andraud*[a]
Three boron diketonate chromophores with extended p-conju-
gated backbone were prepared and their spectroscopic fea-
tures were investigated through a combined theoretical/exper-
imental study. It was shown that these complexes, which un-
dergo very large electronic reorganization upon photoexcita-
tion, combine large two-photon absorption cross section with
an emission energy and quantum efficiency in solution that is
strongly dependent on solvent polarity. The strong positive in-
fluence of boron complexation on the magnitude of the two-
photon absorption was clearly established, and it was shown
that the two-photon absorption properties were dominated by
the quadrupolar term. For one of the synthesized compounds,
intense one- and two-photon-induced solid-state emission
(fluorescence quantum yield of 0.65 with maximum wave-
length of 610 nm) was obtained as a result of antiparallel J-ag-
gregate crystal packing.
1. Introduction
Chromophores that combine large two-photon absorption
cross sections with high solid-state fluorescence quantum
yields are valuable candidates for applications ranging from
optoelectronics (upconversion lasing) to biophotonics (ultra-
bright nanosized fluorescent contrast agent).[1] Yet, reports on
such molecules are relatively scarce in the literature.[2]
thus avoiding the formation of aggregates, which are in the
most general cases detrimental to emission efficiency.[5]
In parallel, the two-photon-induced fluorescence (TPIF) prop-
erties of various boron complexes have been quite extensively
studied by different groups. Besides archetypical boron–dipyr-
romethene (BODIPY), used in bioimaging since the early 2000s
and almost immediately investigated in the context of TPIF,[6]
other types of boron compounds, particularly trivalent ones,
have received considerable attention.[7] In 2003 and 2004 suc-
cessive reports by the groups of Marder and Blanchard-Desce
showed that fluorophores based on b-(diketonato)boron moi-
eties displayed, in spite of a short p-conjugated backbone, un-
expectedly large cross section values up to 200 GM (Gçppert
Meyer unit, 1 GM=10ꢀ50 cm4 sphotonꢀ1).[8]
It was recently established by different groups that boron di-
fluoride complexes of a variety of organic ligands present ex-
ceptional solid-state luminescence properties.[3] It has been
proposed that these exceptional features are most likely a con-
sequence of restrictions of the rotational/torsional mobility
arising from the formation of a boron chelate.[4] Alternatively, it
has also been suggested that steric hindrance induced by the
substituents attached to the boron complex can also partici-
pate in reducing molecular interactions in the crystal packing,
As a consequence, it can be anticipated that similar boron
complexes could constitute an interesting basis to be used as
two-photon solid-state emitters. Indeed, recent studies by
D’Alꢁo, Fages, and co-workers have clearly established that
borylated curcuminoid derivatives are particularly attractive
candidates in this regard, as they combine relatively large two-
photon cross sections with significant fluorescence quantum
yields in solution and in the solid state, with emission that can
reach the near-IR region in the condensed phase.[4f,9]
[a] Dr. P.-H. Lanoꢀ, Dr. B. Mettra, Dr. Y. Y. Liao, Dr. N. Calin, Dr. C. Monnereau,
Dr. C. Andraud
Laboratoire de Chimie UMR CNRS 5182
Ecole Normale Supꢁrieure de Lyon/Universitꢁ de Lyon
46 Allꢁe d’Italie, 69007 Lyon (France)
[b] Dr. A. D’Alꢁo, Prof. F. Fages
CINAM UMR CNRS 7325
In the present paper, we show that a boron complex of 1,3-
diphenylpropane-1,3-dione—a scaffold that has already been
used in the context of solid-state fluorescent materials[10]—for
which both phenyl groups are halogenated in their para posi-
tions, can be used as a convenient and highly reactive elec-
tron-deficient synthetic intermediate towards a variety of two-
photon-absorbing boron diketonate complexes with tunable
absorption and emission wavelengths (labs and lem). We took
Universitꢁ Aix-Marseille
Campus de Luminy, Case 913, 13288 Marseille (France
[c] T. Namikawa, Prof. K. Kamada
IFMRI
National Institute of Advanced Industrial Science and Technology (AIST)
Ikeda, Osaka 563-8577 (Japan)
Supporting Information for this article can be found under http://
ChemPhysChem 2016, 17, 1 – 10
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