Using room temperature phosphorescence of gold(I) complexes for pahs sensing

Article abstract of DOI:10.3390/molecules26092444

The synthesis of two new phosphane-gold(I)–napthalimide complexes has been performed and characterized. The compounds present luminescent properties with denoted room temperature phosphorescence (RTP) induced by the proximity of the gold(I) heavy atom that favors intersystem crossing and triplet state population. The emissive properties of the compounds together with the planarity of their chromophore were used to investigate their potential as hosts in the molecular recognition of different polycyclic aromatic hydrocarbons (PAHs). Naphthalene, anthracene, phenan-threne, and pyrene were chosen to evaluate how the size and electronic properties can affect the host:guest interactions. Stronger affinity has been detected through emission titrations for the PAHs with extended aromaticity (anthracene and pyrene) and the results have been supported by DFT calculation studies.

Full text of DOI:10.3390/molecules26092444

molecules
Article
Using Room Temperature Phosphorescence of Gold(I)
Complexes for PAHs Sensing
Marian Rosental 1 , Richard N. Coldman , Artur J. Moro , Inmaculada Angurell
,2
1
3
1,4
, Rosa M. Gomila 5,
Antonio Frontera 6 , João Carlos Lima 3 and Laura Rodríguez
1,4,
*
1
Department of Inorganic and Organic Chemistry, Inorganic Chemistry Section, Universitat de Barcelona,
Martí i Franquès 1, 08028 Barcelona, Spain; Rosental@stud.uni-heidelberg.de (M.R.);
richard.n.coldham@gmail.com (R.N.C.); inmaculada.angurell@qi.ub.es (I.A.)
2
3
Institute of Inorganic Chemistry, Heidelberg University, Im Neuenheimer Feld 270,
69120 Heidelberg, Germany
LAQV-REQUIMTE, Departamento de Química, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;
artur.moro@gmail.com (A.J.M.); lima@fct.unl.pt (J.C.L.)
Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
Serveis Científico Tècnics, Universitat de les Illes Balears, Crta de Valldemossa km 7.5, 07122 Baleares, Spain;
rosa.gomila@uib.es
4
5
6
Departament de Química, Universitat de les Illes Balears, Crta de Valldemossa km 7.5, 07122 Baleares, Spain;
toni.frontera@uib.es
*
Correspondence: laura.rodriguez@qi.ub.es
Abstract: The synthesis of two new phosphane-gold(I)–napthalimide complexes has been performed
and characterized. The compounds present luminescent properties with denoted room temperature
phosphorescence (RTP) induced by the proximity of the gold(I) heavy atom that favors intersystem
crossing and triplet state population. The emissive properties of the compounds together with the
planarity of their chromophore were used to investigate their potential as hosts in the molecular
recognition of different polycyclic aromatic hydrocarbons (PAHs). Naphthalene, anthracene, phenan-
threne, and pyrene were chosen to evaluate how the size and electronic properties can affect the
host:guest interactions. Stronger affinity has been detected through emission titrations for the PAHs
with extended aromaticity (anthracene and pyrene) and the results have been supported by DFT
calculation studies.
ꢀ
ꢁꢂꢀꢃꢄꢅꢆꢇ
ꢀ
ꢁꢂꢃꢄꢅꢆ
Citation: Rosental, M.; Coldman,
R.N.; Moro, A.J.; Angurell, I.; Gomila,
R.M.; Frontera, A.; Lima, J.C.;
Rodríguez, L. Using Room
Temperature Phosphorescence of
Gold(I) Complexes for PAHs Sensing.
Molecules 2021, 26, 2444. https://
doi.org/10.3390/molecules26092444
Academic Editor: Susana
Keywords: gold(I); polycyclic aromatic hydrocarbons (PAHs); molecular recognition; room tempera-
Ibáñez Maella
ture phosphorescence; DFT
Received: 29 March 2021
Accepted: 18 April 2021
Published: 22 April 2021
1. Introduction
1
,8-Naphthalimides (NI) represent a large family of compounds that are easily tunable
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iations.
and highly thermally and chemically stable. Their well-known photophysical properties
makes them ideal candidates to be explored in different real-life applications such as the
production of organic photochemical dyads and triads, energy storage, light conversion,
gels, hybrid materials, optoelectronic devices, solar cells, sensors, biological applications,
and bioimaging probes among others [1–9].
NI can be easily functionalized allowing not only the possibility to modulate their
emission properties on a large scale [1] but also the design of ligands able to coordinate
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metal atoms giving rise to NI–metal complexes, though these have been less explored than
purely organic NI-derivatives. They are also well known to establish π−π intermolecular
contacts giving rise to the formation of aggregates, affecting their resulting luminescence in
connection with the aggregation induced emission (AIE) and aggregation caused quenching
(
ACQ) concept [
NI-solution samples, phosphorescence may also be achieved in some cases, such as NI-
aggregates or when included within a macrocyclic host [12 14]. The heavy atom effect is
1,6,10,11]. Although fluorescence emission is mainly observed in diluted
–
4
.0/).
Molecules 2021, 26, 2444. https://doi.org/10.3390/molecules26092444
https://www.mdpi.com/journal/molecules

Molecules 2021, 26, 2444
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another way to induce room temperature phosphorescence (RTP) and, to the best of our
knowledge, there are very few examples in the literature in the coordination of NI to heavy
metals to induce RTP emission and all are platinum derivatives [15–17].
In this way, gold(I) emerges as a new route to obtain RTP NI-complexes, since it is well
known to enhance intersystem crossing and triplet state population [18–21]. Nevertheless,
although there are few examples of gold(I)–NI complexes in the literature, they present
fluorescence emission but not phosphorescence [4,22–26].
NI-fluorescence has been used in the molecular recognition of anions, cations and
organic molecules [27–32]. Changes on the RTP emission band for sensing processes has
not been explored in great detail and is a new subject for gold(I)–NI complexes. Hence,
the present investigation focuses on the design and synthesis of new 1,8-naphthalimide
based gold(I) complexes that display RTP and explores their use in molecular recognition
processes. In particular, we are interested in sensing polycyclic aromatic hydrocarbons
(PAHs) since they are well-known environmental contaminants with toxic, mutagenic, and
carcinogenic properties [33 34].. They can be found in different natural sources such as
,
water and soil and are produced from fossil fuels, industrial manufacturing, residential
heating, food preparation, etc. In particular, low molecular weight PAHs (2–3 rings) usually
show a higher concentration in water than high molecular weight PAHs (4–6 rings) since
they present a higher vapor pressure and solubility in water [34]. Their planar aromatic
structure makes them ideal candidates to interact with the NI-core, inducing changes on
the emission properties of the gold(I) complexes used as hosts in an easy and fast process.
Most importantly, the high sensitivity of luminescence will allow the detection of very low
quantities of PAHs.
2. Results and Discussion.
2.1. Synthesis and Characterization
The synthesis of the two new gold(I) complexes containing a naphthalimide chro-
mophore was performed after previous derivatization of the napthalimide group with a
terminal acetylene moiety with slight modifications of the procedure reported in the litera-
ture [35]. It is based on a three steps reaction where the 4-bromo-1,8-naphthalic anhydride
gives the 6-bromo-1H-benzo[de].isoquinoline-1,3(2H)-dione (P1) that will lead to the final
L compound through a Sonogashira reaction (Scheme S1).
The deprotonation of the naphthalimide ligand
by the addition of the stoichiometric amount of [AuCl(PTA)]. or [AuCl(DAPTA)]. (PTA =
,3,5-Triaza-7-phosphaadamantane; DAPTA = 3,7-Diacetyl-1,3,7-triaza-5-phosphabicyclo
3.3.1].nonane) gold(I) sources yields the desired products and in moderate yield (ca.
L with potassium hydroxide followed
1
[
1
2
50%, Scheme 1).
The absence of the terminal alkynyl C C-H proton of L in the IR and NMR spectra of
≡
the complexes confirms the ligand bonds through its alkynyl motif (see Figures S1–S5). A ca.
0
.3 ppm upfield shift of naphthalimide signals and the appearance of the expected pattern
1
of the PTA/DAPTA protons in the corresponding H-NMR spectra confirm the successful
synthesis of the complexes. The 31P-NMR spectra indicate the presence of a main peak at
ca.
−
49 and
−
27 ppm for 1 and 2 respectively in accordance with P-donor coordination
to the metal center [36
,
37]. HRESI-MS spectrometry gives the final evidence of the correct
+
formation of the compounds with the corresponding molecular [M + H]. peaks at m/z
1
575.0922 and 647.1134 for 1 and 2, respectively. The presence of broad signals at H-NMR
31
and additional peaks at P-NMR spectra suggest possible intermolecular aggregation
assemblies, which was confirmed through different methodologies (see below).

Molecules 2021, 26, 2444
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.
Scheme 1. Reaction for the syntheses of the phosphane-gold(I)–napthalimide complexes 1 and 2.
2.2. Photophysical Characterization
Absorption, emission and excitation spectra of
L and complexes 1 and 2 were recorded
in DMSO at 2 × 10− M and the results are summarized in Table 1.
5
Table 1. Absorption and emission (λexc = 418 nm) spectral data of L, 1 and 2 in DMSO.
Absorption λmax (nm)
Compound
Emission λmax (nm)
−
3
−1 −1
(
10 ε (M cm ))
L
1
2
367 (14.1), 349 (15.9)
420 (10.5), 397 (13.9), 370 (9.8)
421 (12.3), 396 (15.9), 372 (12.3)
-
456, 621, 676
457, 621, 675
The absorption spectra of the compounds display a vibronically structured band with
−
1
spacings of 1368 cm corresponding to π−π* intraligand transition of the naphthalim-
ide ligand [ 22 24 38 41]. This band is ca. 50 nm red-shifted upon coordination to the
metal atom, as commonly observed for other chromophores coordinated to the Au(I) unit
Figure 1) [36,37]. The emission of and display two bands, one at ca. 455 nm due to the
intraligand fluorescence emission of the naphthalimide group and another at longer wave-
lengths (ca. 620 nm) attributed to the phosphorescence of the chromophore [12 22 23 39 41].
9
, , , –
(
1
2
,
,
,
,
The phosphorescence assignment is evidenced by the quenching of the intensity of this
emission band in the presence of oxygen (Figure S10) and can be achieved thanks to the
presence of the gold(I) heavy atom that favors the intersystem crossing and population of
the emissive triplet state [42]. The heavy atom effect on room temperature phosphorescence
of gold(I) naphthalimide complexes is reported herein for the first time although it has
previously been observed in platinum complexes, with the similar vibronically structured
shape [39]. Previous luminescent studies with other gold(I)–napthalimide complexes
contain N-substituted napthalimide chromophores and display pure fluorescence emis-
sion [22–26]. In our cases, the naphthalimide group does not present any substitution,
being thus less bulky. Hence, the resulting higher planarity of the ligand in our systems
may favor the approach between different molecules being the chromophore more affected

Molecules 2021, 26, 2444
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by the presence of the heavy atom of the neighbor molecules, affecting the resulting phos-
phorescence emission. No significant emission of
emissive in CH Cl (Figure S11).
L was recorded in DMSO although it is
2
2
Figure 1. Absorption (left) and emission (λexc = 418 nm, right) spectra of L and complexes 1 and 2 in DMSO.
The room temperature phosphorescence (RTP) of the gold(I) complexes may be ob-
served thanks to the presence of the gold(I) atom in the proximity of the chromophore
1
through intermolecular packing. This is in agreement with the corresponding H-NMR of
freshly prepared samples of 1 and 2 (Figures 2 and S12) which display very low intensity
of the aromatic protons, with lower integration values with respect to the rest of the pro-
tons of the molecules, the phosphane moieties, as usually happens in this type of gold(I)
supramolecular assemblies. Thus this serves as direct evidence of the presence of these
aggregation motif [43].
1
Figure 2. H-NMR spectrum of freshly dissolved solution of 1 in DMSO-d .
6

Molecules 2021, 26, 2444
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In fact, intermolecular contacts are expected to happen even at lower concentra-
1
tions than those used for H-NMR and have been verified to start at concentrations of ca.
−
5
−5
10 M (critical aggregation concentrations, c.a.c.) for 1 and 2, respec-
2
× 10
tively, by recording emission spectra at increasing concentrations (Figures S13 and S14).
The lower c.a.c. value of is due to the well-known lower solubility of the PTA phosphane
M
and 5
×
1
compared to DAPTA. Small well-organized aggregates have been also detected by optical
microscopy with cross polarizers (Figure S15).
The molecular electrostatic potential (MEP) of compounds
1 and 2 have been com-
puted through DFT, to investigate the most electron rich and poor regions of the molecule.
The MEP plots are shown in Figure 3, indicating that the most nucleophilic region corre-
sponds to the O-atoms of the naphthalimide unit and the most electrophilic one to the
H-atoms of the phosphine ligands.
Figure 3. MEP surfaces (isovalue 0.001 a.u.) of compounds
1 (a) and 2 (b). The values at selected
points of the surfaces are indicated in kcal/mol.
The MEP is also negative above and below the triple bond and slightly positive at the
Au atom in case of compound 2. The MEP values are small over the naphthalimide unit.
The ability for self-assembly and aggregation of compounds
1 and 2 has been com-
puted from the possible self-assembled dimers. The obtained geometries are given in
Figure 4 and they adopt an antiparallel arrangement where the naphthalimide unit ap-
proaches the phosphane ligand in order to maximize the electrostatic attraction between
the negative O-atoms of naphthalimide and the positive H-atoms of the Au-coordinated
phosphine, in line with the MEP surface analysis. The dimerization energy is larger in
compound
on-top” representation of the assemblies, it can be observed that there is not
in compound and, contrariwise, a small overlap between the -systems of compound
is observed.
1
, in agreement with the larger ability of
1
to form aggregates in DMSO. In the
“
π-overlap
1
π
2

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Figure 4. PB86-D3(COSMO)/def2-TZVP optimized geometries of the self-assembled dimers of
in Å.
1 (a) and 2 (b). Distances
2.3. Molecular Recognition of Polycyclic Aromatic Hydrocarbons, PAHs
The emissive properties of the gold(I) compounds together with the planarity of the
organic chromophore encouraged us to use them as hosts for the molecular recognition
of PAHs, being suitable for detection at very low concentrations. With this goal in mind,
naphthalene, anthracene, phenanthrene, and pyrene, which differ by the number and
position of aromatic rings with an effect on the corresponding size and shape were chosen
as target PAHs. Absorption and emission titrations were performed and the changes on
the spectroscopic properties of the hosts,
1 and 2, were followed upon addition of different
amounts of the corresponding guest. No significant changes were recorded in any case in
the absorption spectra of the host, besides the expected presence of increasing amounts of
guest molecules. More interesting data were retrieved from emission titrations. In general
trends we can observe the formation of 1:2 host:guest adducts and stronger interactions
between the host molecules and PAHs with extended aromaticity present: antracene
pyrene > phenanthrene > naphthalene. Additionally, the resulting adducts with compound
are expected to interact more strongly in agreement with the major decrease in the
≥
2
phosphorescence emission intensity recorded (Table 2, Figures 5 and S16–S23). It must be
stressed that titrations show, in general, two different tendencies: (i) a (fast) first decrease
of the phosphorescence emission (between 0 and 1 equivalent of guest added) and (ii)
a recovery of some of the quenched emission reaching a plateau at 2 equivalents of the
corresponding guest. Considering that the phosphorescence is expected to be enhanced
by the proximity of the chromophore to the gold(I) atom, due to heavy atom effect, the
observed variations let us suggest that the interaction with PAHs, especially with the
anthracene and pyrene, promotes the disruption of homo-aggregates at low concentration
where π···gold or gold···gold interactions are present. At higher concentrations, these
interactions are restored to some extent with the formation of hetero-aggregates. The
different behaviour in the process between host 1 and anthracene may be ascribed to the
phosphorescence recovery at the end of the titration where heteroaggregates are formed
from the interaction of the 1:2 adducts as exemplified in Scheme S2. In particular, it may be
due to the type of the resulting intermolecular contacts. That is, heteroaggregates containing
gold···π or gold···gold interactions in the vicinity of the chromophore are expected to
induce the resulting RTP of the naphthalimide. Thus, either anthracene:1 heterodimers
do not form larger heteroaggregates in the concentration range used or the resulting
aggregates’ geometry do not contain this type of interactions at this concentration range.

Molecules 2021, 26, 2444
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Table 2. Maximum variations (quenching) on the emission intensity of the host
1
or
2
in the titration
with PAHs.
Host/Guest
Anthracene
85%
Naphthalene
<10%
Phenanthrene
88%
Pyrene
60%
1
2
90%
<10%
90%
90%
Figure 5. Emission spectra of
1 (left) and 2 (right) in the presence of different amounts of anthracene. Inset: variations of
the emission maxima at 622 nm against [anthracene].
1H-NMR experiments did not give structural information of the resulting host:guest
adducts since all the host solutions are strongly aggregated at the required NMR concentra-
tions and the peaks are not affected by the addition of the guests (Figures S24–S31).
The calculated geometric and energetic features of 1:1 and 1:2 adducts between hosts
1
and 2 and naphthalene (N), anthracene (A), phenanthrene (Ph), and pyrene (P) are shown
in Figures 6 and 7, respectively. In all cases the binding site is the naphthalimide that forms
stacking interactions with the PAHs. The 1:1 complexes 1···Ph, 1···A, and 1···P exhibit
similar interaction energies (
larger (in absolute value) than that of complex 1···N (
−
14.6,
−
15.0, and
−
15.8 kcal/mol, respectively), which are
−
11.7 kcal/mol, respectively). A
similar trend is observed in the 1:2 complexes, where Ph, A and P exhibit stronger binding
than N. The 1:2 complexes are energetically more favorable than the homodimer 1···1
for Ph, A, and P supporting the disaggregation of the host molecules in the presence of
these PAHs, as displayed through emission titrations. The opposite is observed for N, in
agreement with the absence of interaction detected experimentally for this PAH.
The energies gathered in Figure 6 for the 1:1 and 1:2 complexes suggest that the
binding of the first molecule of PAH has little influence on the binding of the second
molecule of PAH, thus indicating a lack of cooperativity effects.
The optimized geometries of 1:1 and 1:2 complexes of compound
are displayed in Figure 7 and they are similar to those detailed above for compound
The largest 1:1 binding energies are expected for complexes 2···P, 2···A, and 2···Ph with
the calculated energies of 16.3, 15.0, and 14.6 kcal/mol, respectively. Again the
naphthalene complex is the weakest ( 11.9 kcal/mol). A similar trend is observed in the
:2 complexes.
2 with the PAHs
1.
−
−
−
−
1

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Figure 6. PB86-D3(COSMO)/def2-TZVP optimized geometries and binding energies of the dimers 1···N (
···A (c) 1···P (d) and trimers N···1···N (e), Ph···1···Ph (f), A···1···A (g) P···1···P (h).
a), 1···Ph (
b),
1
Figure 7. PB86-D3(COSMO)/def2-TZVP optimized geometries and binding energies of the dimers 2···N (
···A (c) 2···P (d) and trimers N···2···N (e), Ph···2···Ph (f), A···2···A (g) P···2···P (h).
a), 2···Ph (
b),
2

Molecules 2021, 26, 2444
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The reaction energies of the following hypothetical transformations (H···H) + 2
×
PAH
→
2
×
(H···PAH), where
H
stands for hosts
1
and
2
and PAH = N, A, Ph and P, have
also been computed. The corresponding reaction energies for such transformations, namely
Ed1 (for ) and Ed2 (for ), are gathered in Table 2. That is, assuming that the dimer
is the predominant specie in solution, the Ed values give hints about the feasibility to
transform this strong homodimer (1···1 or 2···2) into two heterodimers upon the addition
of one equivalent of PAH (Table 3). It can be observed that in the case of the E1d values
suggest that the three larger A, Ph and P are able to form the 1:1 hetero-dimers (exothermic
process). In the case of , the E2d values are in all cases negative, thus suggesting that
∆
1
∆
2
∆
1
∆
2
∆
all PAHs should be able to form the host–guest complexes. However, the value is very
small for N compared to the others, which is in line with the experimental findings that
detect a weak binding for N. In addition, we have also calculated the formation of the
heterotrimers using similar transformations: (H···H) + 4
The corresponding reaction energies for such transformations, where two equivalents of
PAH are added, namely, Et1 (for ) and Et2 (for ), are also summarized in Table 2. All
×
PAH
→
2
× (PAH···H···PAH).
∆
1
∆
2
reactions are exothermic, thus suggesting than the addition of an excess of PAH should
provoke the transformation of the homodimer into the heterotrimer (PAH···H···PAH).
Inspection of Table 3 lets us to observe a direct trend between
∆E and the number of
aromatic rings, with more negative
∆E values as the number of rings increases (2 for N, 3
for Ph and A with similar ∆E, and 4 for P) for both the heterodimers and heterotrimers.
Table 3. Formation energies of the heterodimers (
in kcal/mol for hosts 1 and 2.
∆
Ed1 and
∆
Ed2) and heterotrimers (
∆
Et1 and ∆E )
t2
Compound 1
PAH
Compound 2
∆
Ed1
∆Et1
∆Ed2
−2.7
−7.9
−8.8
−11.5
∆Et2
N
Ph
A
+0.8
−4.7
−5.8
−7.2
−22.4
−32.8
−34.0
−37.0
−25.8
−36.9
−36.4
−43.9
P
3. Conclusions
The self-assembly of phosphane-gold(I)–naphthalimide complexes gives rise to strong
−
5
aggregates in solution even at very low concentrations (~10 M). Nevertheless, the com-
pounds show a higher affinity to interact with long PAHs compounds, such as anthracene
and pyrene. This interaction induces a disassembly of the gold(I) complexes to form very
sTable 1:2 (host:guest) adducts. The smaller naphthalene PAH induces little effect on the
spectroscopic properties of naphthalimide–gold(I) complexes, indicating that the estab-
lished π–π interactions with naphthalimide are not strong enough to promote disassembly
of these gold(I) complexes.
DFT calculations suggest intermolecular contacts in a head to tail disposition of the
gold(I) complexes with Au···π or Au···N-H interactions. The proximity of the gold(I) heavy
atom to the naphthalimide chromophore must be the responsible for the observed room
temperature phosphorescence emission of the hosts.
4. Materials and Methods
4.1. General Procedures
All manipulations have been performed under prepurified N using standard Schlenk
2
techniques. Dry solvents were dispensed from a solvent purification system (Innova-
tive Technologies; Newburyport, MA, USA). Commercial reagents 4-bromo-naphthalic
anhydride (Merck, Darmstadt, Germany, 95%), Ammonium hydroxide solution (A.C.S
reagent, 28–30%), ethynyltrimethylsilane (Merck, 98%), Copper (I) iodide (Merck, 98%),
triethylamine (Merck, 99.5%), 1,3,5-triaza-7-phosphaadamantane (Merck, 97%), tetrabuty-

Molecules 2021, 26, 2444
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lammonium fluoride (TBAF, 1M in tetrahydrofuran, Panreac), naphthalene (Koch-Light
Labs, Haverhill, UK), anthracene (
pyrene (≥99%, Merck) were used as received.
≥
99%, Merck), phenanthrene (
≥
99.5%, Merck), and
4
.2. Physical Measurements
1
Infrared spectra have been recorded on a FT-IR 520 Nicolet Spectrophotometer. H
(TMS) = 0.0 ppm) and 31P{ H} NMR (
1
δ
(85% H PO ) = 0.0 ppm) spectra have been
NMR (
δ
3
4
obtained on a Varian Mercury 400, Bruker 400, and Bruker 500. ES(+) mass spectra were
recorded on a Fisons VG Quatro spectrometer. Absorption spectra have been recorded on a
Varian Cary 100 Bio UV-Spectrophotometer and emission spectra on a Horiba-Jobin-Ybon
SPEX Nanolog Spectrofluorimeter.
4.3. Theoretical Methods
The calculations of the dimers and trimers were performed at the DFT level of theory
using PB86 functional [44] the def2-TZVP basis set [45] and the D3 dispersion correction
e4we [46] with the help of the Turbomole 7.0 program package [47]. Solvent effects
were considered using COSMO (solvent DMSO) during the optimization [48]. The MEP
surfaces were computed at the PB86-D3/def2-TZVP level of theory and visualized using
the Gaussview [49] and using the cubes generated by the Multiwfn software [50] and the
wavefunction obtained using Turbomole 7.0 (TURBOMOLE GmbH, Karlsruhe, Germany).
4.4. Absorption and Emission Titrations
Absorption and emission spectra were recorded using a quartz cuvette with a path
length of 10
×
10 mm and a volume of 3 mL. All solutions were prepared with dry
DMSO, diluted from a more concentrated stock solution, and used on the same day they
were prepared.
4.5. Synthesis and Characterization
Synthesis of 6-Bromo-1H-benzo[de].isoquinoline-1,3(2H)-dione (P1)
The synthesis of this compound was adapted from the previous reported in the
literature [35].
-Bromo-1,8-naphthalic anhydride (507 mg, 1.83 mmol, 1 eq.) was suspended in EtOH
10 mL) and 1.50 mL of a 20% NH solution was added. The mixture was refluxed for 3 h,
4
(
3
cooled down to r.t., filtrated and washed with EtOH giving a beige solid (429 mg, 85%).
1
H-NMR (400 MHz, CDCl3):
H), 8.08 (d, J = 7.9 Hz, 1H), 7.88 (t, J = 7.9 Hz, 1H). ESI-MS(+): m/z = calc. 275.97 [M + H]. ,
δ
= 8.65 (m, J = 8.4 Hz, 2H), 8.52 (s, 1H), 8.42 (d, J = 7.9 Hz,
+
1
found 275.97.
Synthesis of 6-((Trimethylsilyl)ethynyl)-1H-benzo[de].isoquinoline-1,3(2H)-dione (P2
-Bromo-1H-benzo[de].isoquinoline-1,3(2H)-dione (299 mg, 1.08 mmol, 1.00 eq.) was
suspended in dry THF (8 mL) under N atmosphere and TMS-acetylene (150 mg, 1.53 mmol,
)
6
2
1
.40 eq.) in THF (2 mL) was added. CuI (20 mg, 6 mol%) and [PdCl (PPh ) ]. (18 mg,
2 3 2
3
mmol) were dissolved in dry THF (5 mL) and NEt (6 mL) was added, then the mixture
3
was added to the previous one and left stirring overnight. DCM (20 mL) was added and the
precipitate removed by filtration. The organic layer was washed with sat. NH Cl solution
4
(
3
×
10 mL), water (2
×
10 mL), and brine (10 mL), dried over MgSO and concentrated in
4
vacuum. Purification by column chromatography (SiO , DCM/acetone [10:1]., v/v) yielded
P2 as yellow solid (180 mg, 57%). H-NMR (400 MHz, CDCl ):
2
1
δ = 8.69 (d, J = 8.4 Hz, 1H),
3
8
7
.63 (d, J = 7.3 Hz, 1H), 8.52 (dd, J = 7.6, 1.1 Hz, 1H), 7.91 (d, J = 7.6 Hz, 1H), 7.84 (dd, J = 8.2
.5 Hz, 1H), 0.37 (s, 9H).
Synthesis of 6-Ethynyl-1H-benzo[de].isoquinoline-1,3(2H)-dione (L)
-((Trimethylsilyl)ethynyl)-1H-benzo[de].isoquinoline-1,3(2H)-dione was dissolved in
THF (10 mL) and water (1 mL) was added. 1 M TBAF solution in THF (1.25 mL, 1.25 mmol,
.22 eq.) was added at r.t. and the orange mixture was stirred for 3 h. Water (5 mL) was
added and a precipitate formed. The mixture was extracted with DCM (4 10 mL) and
,
6
2
×

Molecules 2021, 26, 2444
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washed with water (2
×
10 mL) and brine (10 mL), then dried over MgSO . After removing
4
the solvent in vacuum, the solid was washed with hexane and Et O, yielding
L
as pale
= 8.73 (dd, J = 8.4, 1.2 Hz, 1H),
.64 (dd, J = 7.6, 1.2 Hz, 1H), 8.53 (d, J = 7.6 Hz, 1H), 8.41 (bs, 1H), 7.97 (d, J = 7.6 Hz, 1H),
2
1
ochre solid (64 mg, 51%). H-NMR (400 MHz, CDCl ):
8
7
δ
3
1
.86 (dd, J = 8.4, 7.6 Hz, 1H), 3.76 (s, 1H). H NMR (500 MHz, dmso-d ):
δ = 11.84 (s, 1H,
6
NH), 8.64 (dd, J = 8.4, 1.2 Hz, 1H), 8.51 (dd, J = 7.6, 1.2 Hz, 1H), 8.40 (d, J = 7.6 Hz, 1H), 8.05
(
d, J = 7.6 Hz, 1H), 7.98 (dd, J = 8.4, 7.6 Hz, 1H), 5.09 (s, 1H). 13C-NMR (125 MHz, dmso-d6):
δ
= 164.1(CO), 163.8 (CO), 131.8 (CH), 131.7 (CH), 131.6, 130.7, 129.4 (CH), 128.7, 128.5 (CH),
◦
125.7, 123.2, 123.0, 90.3 (CCH), 80.3(CCH). Melting point: 296–298 C.
Synthesis of [Au(L)(PTA)]. (1)
L
(30 mg, 0.14 mmol, 1.00 eq.) and KOH (40 mg, 0.68 mmol, 5.00 eq.) were suspended
in dry MeOH (5 mL) under N atmosphere and stirred for 30 min. [AuCl(PTA)]. (53 mg,
2
0.14 mmol, 1.00 eq.) was suspended in dry DCM (5 mL) and added to the other solution
leading to the formation of a yellow precipitate. The mixture was stirred overnight, then
filtrated through a glass funnel, washed with acetonitrile (10 mL) and Et O (10 mL) and
2
1
dried in vacuum. [Au(
400 MHz, DMSO-d6):
H), 7.81 (dd, J = 8.4 Hz, J = 7.2 Hz, 1H), 7.68 (d, J = 7.6 Hz, 1H), 4.52–4.32 (m, 12H).
L)(PTA)]. (
1
) was obtained as yellow solid (55 mg, 70%). H-NMR
(
1
δ = 8.57 (d, J = 8.4 Hz, 1H), 8.33 (d, J = 7.2 Hz, 1H), 8.20 (d, J = 7.6 Hz,
3
1
P
NMR (162 MHz, DMSO-d ):
δ
=
−
49.5.0 (s),
−
20 (s). ESI-MS(+): m/z = calc. 575.0866
6
+
[
M+H]. , found 575.0922.
Synthesis of [Au(L)(DAPTA)]. (2)
(23 mg, 0.10 mmol, 1.00 eq.) and KOH (19 mg, 0.634 mmol, 3.00 eq.) were suspended
in dry MeOH (8 mL) under N atmosphere and stirred for 30 min. [AuCl(DAPTA)]. (48 mg,
L
2
0.10 mmol, 1.00 eq.) was suspended in dry DCM (5 mL) and added to the other solution
leading to the formation of a yellow precipitate. The mixture was stirred overnight, then
filtrated through a glass funnel, washed with acetonitrile (10 mL) and Et O (10 mL) and
2
1
dried in vacuum. [Au(
NMR (400 MHz, DMSO-d6)
d, J = 7.2 Hz, 1H), 7.80 (dd, J = 8.0 Hz, J = 7.2 Hz, 1H), 7.64 (d, J = 7.2 Hz, 1H), 5.50 (d,
J = 13.6 Hz, 1H), 5.40 (m, 1H), 4.90 (m, 1H), 4.61 (d, J = 14 Hz, 1H), 4.30 (d, J = 15.6 Hz, 1H),
L
)(DAPTA)]. (
2
) was obtained as yellow solid (46 mg, 68%). H-
δ
= 8.63 (d, J = 8.0 Hz, 1H), 8.33 (d, J = 7.2 Hz, 1H), 8.19
(
31
4
.09 (d, J = 14 Hz, 1H), 4.03 (s, 2H), 3.77 (d, J = 16 Hz, 1H). P-NMR (162 MHz, DMSO-d6)
+
δ = –26.9 (s). ESI-MS(+): m/z = calc. 647.1078 [M + H]. , found 647.1134.
1
Supplementary Materials: The following are available, Figure S1: H NMR spectrum of P1 in CDCl ,
3
1
1
Figure S2: H NMR spectrum of P2 in CDCl , Figure S3: H NMR spectra of L in CDCl and DMSO-
3
3
L
1
3
d ,Figure S4: C-NMR spectrum of
L
in DMSO-d , Figure S5: HSQC NMR spectrum of in DMSO-d6,
1 in DMSO-d , Figure S7: P{ H} NMR spectrum of 1 in DMSO-d6,
6
6
6
1
31
1
Figure S6: H-NMR spectrum of
Figure S8: H-NMR spectrum of
1
31
1
2
in DMSO-d , Figure S9: P{ H} NMR spectrum of
2
in DMSO-
6
d6, Figure S10: Absorption and emission spectra of
1 and 2 in air-equilibrated and N -saturated
2
−
4
solutions, Figure S11: Absorption and Emission spectra of
L
in dichloromethane at 2 × 10
M
1
concentration (λexc = 330 nm), Figure S12: H-NMR spectrum of freshly dissolved solution of
2
in DMSO-d , Figure S13: Emission spectra
1
at different concentrations in DMSO (λexc = 370 nm)
at different concentrations in DMSO (λexc = 370 nm). Inset: Plot
of the intensity of the emission at 435 nm against concentration, Figure S15: Optical microscopy
images of (A) and (B) in DMSO at c.a.c., Figure S16: Absorption spectra of in the presence of
different amounts of anthracene, Figure S17: Absorption and Emission spectra of in the presence
of different amounts of naphthalene. Inset: variations of the emission maxima at 622 nm against
naphthalene], Figure S18: Absorption and Emission spectra of in the presence of different amounts
of phenanthrene. Inset: variations of the emission maxima at 622 nm against [phenanthrene],
Figure S19: Absorption and Emission spectra of in the presence of different amounts of pyrene.
Inset: variations of the emission maxima at 622 nm against [pyrene], Figure S20: Absorption spectra
,
6
Figure S14: Emission spectra of
2
1
2
1
1
[
1
1
of
of
2
2
in the presence of different amounts of anthracene, Figure S21: Absorption and Emission spectra
in the presence of different amounts of naphthalene. Inset: variations of the emission maxima
at 622 nm against [naphthalene], Figure S22: Absorption and Emission spectra of
2 in the presence
of different amounts of phenanthrene. Inset: variations of the emission maxima at 622 nm against

Molecules 2021, 26, 2444
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[
phenanthrene], Figure S23: Emission spectra of
2
in the presence of different amounts of pyrene.
1
Inset: variations of the emission maxima at 622 nm against [pyrene], Figure S24: H NMR spectra in
DMSO-d of
of
pyrene and 1:1 adduct 1: pyrene, Figure S27: H NMR spectra in DMSO-d of
and 1:1 adduct 1: phenanthrene, Figure S28: H NMR spectra in DMSO-d of
adduct 2:anthracene, Figure S29: H-NMR spectra in DMSO-d of
2
1
1, anthracene and 1:1 adduct 1:anthracene, Figure S25: H NMR spectra in DMSO-d
6
6
1
1
, naphthalene and 1:1 adduct 1: naphthalene, Figure S26: H NMR spectra in DMSO-d of
1,
6
1
1, phenanthrene
6
1
2, anthracene and 1:1
6
1
2, naphthalene and 1:1 adduct
6
1
: naphthalene, Figure S30: H NMR spectra in DMSO-d of
2, pyrene and 1:1 adduct 2: pyrene,
6
1
Figure S31: H NMR spectra in DMSO-d of
Experimental procedure for the synthesis of
2
, phenantrene and 1:1 adduct 2: phenantrene, Scheme S1:
, Scheme S2: Schematic representation of the possible
6
L
rationalization of the different steps of the host:guest interaction and resulting aggregates.
Author Contributions: M.R.; R.N.C.; A.J.M.; I.A.: synthesis and characterization of the complexes;
photophysical characterization and absorption and emission titrations. R.M.G. theoretical calcula-
tions. A.F.: supervision and report of the theoretical calculations results. J.C.L. supervision and
support on the photophysical data. L.R., global supervision of all the work and redaction of the
manuscript. All authors have read and agreed to the published version of the manuscript.
Funding: The authors are grateful to the Spanish Ministerio de Ciencia, Innovación y Universidades
(
AEI/FEDER, UE Projects CTQ2016-76120-P and PID2019-104121GB-I00). This work was supported
by the Associate Laboratory for Green Chemistry—LAQV which is financed by national funds from
FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020). R.C. and M.R. are also indebted to Erasmus
Exchange Program. Authors would also like to acknowledge COST Actions CA1740—Nano4clinics
and CA18202—NECTAR, International Research Network Hetero-elements and Coordination Chem-
istry: from Concepts to Applications (HC3A) and Spanish network Materiales Supramoleculares
Funcionales (RED2018-102331-T).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: The data presented in this study are available on request from the
corresponding author.
Conflicts of Interest: The authors declare not conflicts of interest.
Sample Availability: Samples of the compounds L, 1 and 2 are available from the authors.
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