Schiff bases-titanium (III) & (IV) complex compounds: Novel photocatalysts in Buchwald-Hartwig C–N cross-coupling reaction

Article abstract of DOI:10.1016/j.jphotochem.2021.113346

Nine novel Schiff bases were derived from salicylic aldehyde and oxalic aldehyde, isolated, and their molecular and spatial structure were explored by a set of experiments (IR, CNMR, HNMR, CHN, SEM, XRD) and theoretical simulation (DFT def2-TZVP). A high potential was predicted in metal cations chelating. The isolated organic species were applied as the ligands in the reaction of complex formation with titanium (III) chloride and (IV) bromide and 12 novel complexes were synthesized and studied experimentally and theoretically. Using the UV–vis spectroscopic titration, the solution stability of the complexes was indicated. Depending on the nature of the Schiff base ligand, their formation constants were calculated in the range of 6.84–17.32. Using the DFT def2-TZVP theoretical method together with the experimental spectroscopic data, the coordination types of the ligands were investigated, and the structure of the complexes was proposed. The photocatalytic ability of the isolated complexes was tested in the C-N cross-coupling reaction under sunlight. Complexes exhibited high visible-light photocatalytic activity for a wide range of aromatic and benzylic amines including electron-withdrawing and electron-donating groups from moderate to good yields ranging in 50–85 %. The use of an inexpensive, clean, and renewable energy source (visible light) is the superiority of the developed photocatalytic systems.

Full text of DOI:10.1016/j.jphotochem.2021.113346

Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Contents lists available at ScienceDirect
Journal of Photochemistry & Photobiology, A: Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Schiff bases-titanium (III) & (IV) complex compounds: Novel photocatalysts in
Buchwald-Hartwig C–N cross-coupling reaction
,
,
Yahya Absalana *, Nazanin Noroozi Shada, Mostafa Gholizadeha *, Ghodrat Mahmoudib,
Hossein Sabet Sarvestania, Pavel Strashnovc, Khashayar Ghandid, Olga Kovalchukovac
a Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
b Department of Chemistry, Faculty of Science, University of Maragheh, P.O. Box 55136-553, Maragheh, Iran
c Department of General Chemistry, RUDN University, 6, Miklukha-Maklaya St, Moscow, 117198, Russian Federation
d Department of Chemistry, University of Guelph, 50 Stone Road East Guelph, Ontario, N1G 2W1, Canada
A R T I C L E I N F O
A B S T R A C T
Keywords:
Nine novel Schiff bases were derived from salicylic aldehyde and oxalic aldehyde, isolated, and their molecular
and spatial structure were explored by a set of experiments (IR, CNMR, HNMR, CHN, SEM, XRD) and theoretical
simulation (DFT def2-TZVP). A high potential was predicted in metal cations chelating. The isolated organic
species were applied as the ligands in the reaction of complex formation with titanium (III) chloride and (IV)
bromide and 12 novel complexes were synthesized and studied experimentally and theoretically. Using the
UV–vis spectroscopic titration, the solution stability of the complexes was indicated. Depending on the nature of
the Schiff base ligand, their formation constants were calculated in the range of 6.84–17.32. Using the DFT def2-
TZVP theoretical method together with the experimental spectroscopic data, the coordination types of the li-
gands were investigated, and the structure of the complexes was proposed. The photocatalytic ability of the
isolated complexes was tested in the C-N cross-coupling reaction under sunlight. Complexes exhibited high
visible-light photocatalytic activity for a wide range of aromatic and benzylic amines including electron-
withdrawing and electron-donating groups from moderate to good yields ranging in 50–85 %. The use of an
inexpensive, clean, and renewable energy source (visible light) is the superiority of the developed photocatalytic
systems.
Complex compounds
Buchwald-Hartwig reaction
Visible-light photocatalyst
Titanium bromide (IV)
Titanium chloride (III)
1. Introduction
proper substrate for the preparation of several pharmaceuticals at in-
dustrial scales [6–14]. Catalyzed amination of different halides and
The Buchwald–Hartwig amination is a famous organic reaction in
carbon-nitrogen coupling through the use of palladium, as the main and
usual catalyst, to couple amines with aryl halides [1–4]. This
well-known reaction forms a bond between carbon and nitrogen and is
highly useful in the synthesis of arylamines for both industrial and
research purposes [5].
pseudo-halides has been enhanced and quickly inserted with a suitable
ratio to obtain new materials, heterocyclic systems, and pharmaceuti-
cals. It has been recognized as a useful tool for the synthesis of biological
compounds [6,15–20].
Such an incredible usage of this method can be assigned to the
domination of aromatic amines, which can serve as precursor substances
and their importance in biologically active materials [21] (i.e. highly
important and vital groups such as kinase inhibitors [22,23], antibiotics
[24] and CNS active agents [25]).
Numerous reactions are challenged by serious limitations such as
functional group tolerance and substrate area. Thanks to the Buchwald-
Hartwig reaction, various generations of catalyst complex have been
presented, each allowing premier area in connecting associations and
gentle reaction situation, offering all amines the possibility of figurative
connection with various types of aryl-connecting agents.
In the process of ligands isolation, a similar approach was selected in
Shiff bases isolation. The reactants were used to isolate a variety of the
potential ligands with different steric properties of the organic species.
The changes in the oxidation state of the metal cation (Ti+3 or Ti+4) can
lead to different types of electronic and magnetic properties in the
Aryl carbon-nitrogen bonds can be found in natural compounds,
affecting the entire synthesis of natural compounds and providing a
* Corresponding authors.
E-mail addresses: Yahyaabsalan2014@gmail.com (Y. Absalan), m_gholizadeh@um.ac.ir (M. Gholizadeh).
https://doi.org/10.1016/j.jphotochem.2021.113346
Received 22 February 2021; Received in revised form 10 April 2021; Accepted 5 May 2021
Available online 11 May 2021
1010-6030/© 2021 Elsevier B.V. All rights reserved.

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
isolated metal complexes. The formation of coordination spheres and
multifunctionality of the ligands may result in the formation of coordi-
nation polymers with high activities in different catalytic processes. This
reflects the key role of the ligands in this type of reaction their influence
on the reaction speed and even temperature. Different types of ligands
have been employed in this reaction among which, BINAP [26–29], dppf
[30–34], and Xantphos [35–39] can be mentioned. Electron donation
plays a key role in this reaction in the favor of the ligand to place
phosphines in the first position; Josiphos [40–45], N-heterocyclic car-
benes [46–51], and trialkyl phosphines [52–55] are some remarkable
instances of electron donation which can increase the substrate area [9,
56].
method with the Grimme D3 dispersion correction with the Becke-
Johnson damping scheme (D3BJ) was employed for single-point calcu-
lations [82]. The Ahlrichs’ def2-TZVP basis set [83] was used. To study
the effect of titanium salts on the ligand in an aqueous environment,
UV–vis spectroscopy in the range of 200ꢀ 800 nm was used by a Cary-50
scan spectrophotometer (Varian). FT-IR spectra were recorded on
pressed KBr pellets using an AVATAR 370 FT-IR spectrometer (Therma
Nicolet spectrometer, USA) at room temperature in the wavenumber
range of 4000ꢀ 400 cmꢀ 1 at a resolution of 4 cmꢀ 1. NMR spectra were
taken using an NMR Bruker Avance spectrometer at 300 and 400 MHz in
CDCl3 or DMSO. Mass spectra were recorded with a CH7A Varianmat
Bremem instrument at 70 eV electron impact ionization, in m/z (rel %).
CHN elemental analyses were performed by elemental Thermo Finnigan
Flash EA microanalyses whose results were in good agreement (±0.3 %)
with the calculated values. All yields refer to the isolated products after
purification by column chromatography. The photocatalytic coupling
experiments were conducted in a capped-sealed test tube.
Although many systems, with the mentioned characters, can be used
as catalyzed C-N coupling agents just a limited number of groups work
properly. This is directly effective on the feasibility of the catalytic
system, its forcefulness, accessibility of substrate, and ligand range [57].
Numerous studies [12,58,67–70,59–66] have addressed other types
of ligands to find a suitable condition for an efficient catalyst to be used
in a broad range of reactions. Palladium-catalyzed amination Suzuki
cross-coupling reaction [71–75], etherification of aryl halides [76], and
arylation of enolates [77–81] are some of the well-known instances.
Although the Buchwald-Hartwig reaction was developed to include a
group of coupling associations, the situation required for any particular
reactants is yet substrate-dependent.
2.2. Synthesis of Ligand
2.2.1. 6,6′-((1E,1′E)-(pyridine-2,6-diylbis(azaneylylidene))bis
(methaneylylidene))bis(2-((E)-phenyldiazenyl)phenol) (L1)
2-hydroxy-3-(phenyldiazenyl)benzaldehyde as an Azo-linked start-
ing material for the synthesis of L1 is synthesized by the reaction of
aniline and salicylaldehyde (1). To a water (20 mL) solution of aniline
(0.93 g, 10 mmol) hydrochloric acid (2.5 ml) was added and heated to
70 ◦C. The mixture was diazotized with dropwise adding sodium nitrite
(0.97 g, 14 mmol) dissolved in water (5 mL) between 0 ◦C–5 ◦C. Then a
solution of salicylaldehyde (1.06 mL, 10 mmol) in water (19 mL) con-
taining NaOH (3.99 g, 10 mmol) was added very slowly in 1 h at 0 ◦C.
The mixture was vigorously stirred for 30 min. The brown solid product
was collected by filtration and washed with ethanol and dried under
vacuum at 80 ◦C overnight. Finally the pure product was recrystallized
from ethanol.
Here, a novel photo-catalyst was derived through new Schiff base
ligands and titanium salts (III, IV), as central ions, under visible radia-
tion at room temperature to be applied in the Buchwald–Hartwig ami-
nation reaction. By offering donor bonds with titanium metal, ligands
changed the energy bandgap toward the visible range. The reaction was
carried out between bromobenzene and aromatic amines. The novelties
of this research include the synthesis of new groups of Schiff bases, usage
of titanium salt (as a cheap and non-poisoning metal) for the first time,
and presenting an eco-friendly condition using inexpensive, clean, and
renewable visible light as an energy source with proper photocatalytic
activity, short reaction time, and excellent yield.
2. Experiment
2.1. Materials and characterization
All the precursors, including organic precursors, solvents, and salt
metals were purchased from Sigma-Aldrich (≥ 98%) and used as
received without further purification. The purity determinations of the
products and the progress of the reactions were accomplished by TLC on
silica gel Polygram STL G/UV 254 plates. The melting points of the
products were determined with an Electrothermal Type 9100 melting
point apparatus. X-ray powder diffraction (XRD) was performed using a
Then,
a mixture of 2-hydroxy-3-(phenyldiazenyl)benzaldehyde
(2.26 g, 10 mmol) and 2,6-diaminopyridine (0.54 g, 5 mmol) was dis-
solved in ethanol (20 mL). The solution was refluxed for 2 h. Then it was
cooled at room temperature and filtered the mixture. A red solid product
has been obtained in the pure form (2). Further purification was gained
PANalytical Company X’Pert Pro MPD diffractometer with Cu Kα radi-
by recrystallization from ethanol. M.p.: 263 ◦C; FT-IR (KBr disk):
ν 3339,
ation (λ =0.154 nm) radiation. FE-SEM images were obtained from a
TESCAN, Model: MIRA3 scanning electron microscope operating at an
acceleration voltage of 30.0 kV (manufactured by the Czech Republic).
The electronic structure calculations were carried out with the ORCA
program package ver. 4.1.1. Geometry optimizations were performed
using composite approach B97-3c, while wB97 M density functional
3058, 1711, 1608, 1595, 1481, 1446, 1405, 1352 cmꢀ 1. MS m/z: 525.19
(M+). Anal. Calcd. For C31H23N7O2: C, 70.84; H, 4.41; N, 18.66; Found:
C, 68.22; H, 4.15; N, 17.5 %.
2.2.2. 5,5′-Methylenebis(2-hydroxybenzaldehyde)
It is used as a common starting material for the synthesis of L2, L3
2

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
ligands. 5,5′-Methylenebis(2-hydroxybenzaldehyde) is synthesized by
the reaction of salicylaldehyde (12.2 g, 100 mmol) and formaldehyde
(1.5 g, 50 mmol) in glacial acetic acid (20 mL) at room temperature.
Then concentrated sulfuric acid (1.0 mL, catalytic) was slowly added to
the suspension and the reaction mixture was then allowed to stir at 90 ◦C
for 4 h. After completion of the reaction it was poured on iced water to
form the solid product that was collected by filtration and washed with
water and hexane. The crude product was obtained as an off-white solid
(3).
2.2.5. 2,2′-((1E,1′E)-((2,2-dimethylpropane-1,3diyl)bis(azaneylylidene))
bis(methaneylylidene)) diphenol (L4)
For the synthesis of Schiff base ligand (L4), the methanolic solution
(10 mL) of 2,2-Dimethyl-1,3-diaminopropane (0.10 g, 1 mmol) was
added to the methanolic solution (10 mL) of 2-hydroxybenzaldehyde
(0.24 g, 2 mmol). After stirring (30 min) of the resulting solution at
room temperature, a yellow sediment was obtained and separated by
vacuum filtration, washed with methanol and dried in a desiccator (6).
M.p.: 86 ◦C; 1H NMR (300 MHz, DMSO): δ 1.12 (t, J = 6, 6H, CH3), 3.53
(s, 4H, CH2), 6.90–7.39 (m, 8H, Ar), 8.38 (s, 2H, C = N), 13.60 (s, 2H,
OH, D2O exchangeable; 13C NMR (75 MHz, DMSO): δ 24.41, 36.2, 68.1,
116.9, 118.6, 118.7, 131.3, 132.3, 161.2, 165.7; FT-IR (KBr disk):
ν
3064, 3005, 2962, 2881, 2831, 2725, 1631, 1580, 1497, 1275 cmꢀ 1; MS
m/z: 310 (M+). Anal. Calcd. For C19H22N2O2: C, 73.52; H, 7.14; N, 9.03;
Found: C, 71.2; H, 6.95; N, 9.26 %.
2.2.6. (Z)-N’-(2-hydroxy-1,2-diphenylethylidene)isonicotinohydrazide
(L5)
2.2.3. 4,4′-methylenebis(2-((E)-((2-hydroxyphenyl)imino)methyl)phenol)
(L2)
To a stirring solution of 2-Hydroxy-2-phenylacetophenone (2.12 g,
10 mmol) in ethanol (20 mL), 4-pyridinecarboxylic acid hydrazide
(1.37 g, 10 mmol) was added. Then glacial acetic acid (0.1 mL, as a
catalyst) was slowly added to the reaction mixture was then allowed to
stir at 75 ◦C for 5 h. Then it has been cooled at room temperature and
A mixture of 5,5′-Methylenebis(2-hydroxybenzaldehyde) (2.05 g,
8 mmol) and o-aminophenol (1.75 g, 16 mmol) was dissolved in ethanol
(20 mL). The solution was refluxed for 60 min. Then it has been cooled
at room temperature and filtered the mixture. An orange solid product
has been obtained in the pure form (4). Further purification was gained
by recrystallization from ethanol. M.p.: 226 ◦C; 1H NMR (300 MHz,
DMSO): δ 3.91 (s, 2H, CH2), 6.85–7.48 (m, 14H, Ar), 8.94 (s, 2H, C = N),
9.72 (s, 2H, OH, D2O exchangeable), 13.62 (s, 2H, OH, D2O exchange-
able); 13C NMR (75 MHz, DMSO): δ 116.9, 117.2, 119.7, 120, 128.4,
1
filtered the solid product in the pure form (7). M.p.: 111 ◦C; H NMR
(300 MHz, DMSO) δ 10.15 (s, 1 H), 8.86 (s, 1 H), 8.73 (d, J =5.1 Hz,
2 H), 8.03 (d, J =7.7 Hz, 2 H), 7.77 (d, J =5.1 Hz, 2 H), 7.58 (t, J
=7.3 Hz, 1 H), 7.46 (q, J =7.4 Hz, 4 H), 7.33 (t, J =7.4 Hz, 2 H), 7.25 (t,
J =7.2 Hz, 1 H), 6.11 (q, J = 6.3, 5.6 Hz, 2 H), 4.73 (s, 2 H), 4.54 (s,
1 H). 13C NMR (75 MHz, DMSO) δ 199.68, 164.41, 150.69, 140.76,
140.23, 135.21, 133.71, 129.33, 129.07, 128.96, 128.19, 127.78,
132, 132.3, 133.8, 135.4, 151.5, 159.5, 161.9; FT-IR (KBr disk): ν 3043,
2896, 2831, 1636, 1592, 1490, 1459, 1275, 1137 cmꢀ 1; MS m/z: 438
(M+). Anal. Calcd. For C27H22N2O4: C, 73.96; H, 5.06; N, 6.39; Found: C,
72.47; H, 4.79; N, 5.39 %.
126.92, 121.50, 76.17. FT-IR (KBr disk):
ν 3413, 3059, 2933, 1676,
1596, 1458, 1263 cmꢀ 1; MS m/z: 333 (M+). Anal. Calcd. For
C20H19N3O2: C, 72.49; H, 5.17; N, 12.68; Found: C, 72.20; H, 5.62; N,
2.2.4. N’,N”’-((1E,1′E)-(methylenebis(6-hydroxy-3,1-phenylene))bis
12.51 %.
(methaneylylidene)) di(benzohydrazide) (L3)
To a stirring solution of benzhydrazide (2.17 g, 16 mmol) in ethanol
(15 mL), 5,5′-methylene-bis-salicylaldehyde (2.05 g, 8 mmol) was
added. The mixture then refluxed for 4 h. The white solid was filtered-
off and washed with ethanol and dried over CaCl2 (5). The crude
product was purified by recrystallization from ethanol.
2.2.7. 2,2′-((1E,1′E)-(((1E,2E)-1,2-diphenylethane-1,2-diylidene)bis
(hydrazine-2,1-diylidene)) bis(methaneylylidene))diphenol (L6)
To a stirring solution of salicylaldehyde (2.44 g, 20 mmol) in ethanol
(20 mL), Benzyl Dihydrazone (2.38 g, 10 mmol) was added. Then
glacial acetic acid (0.1 mL, as a catalyst) was slowly added to the re-
action mixture was then allowed to stir at 75 ◦C for 6 h. Then it has been
3

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
cooled at room temperature and filtered the solid product in the pure
form (8). M.p.: 193 ◦C; 1H NMR (300 MHz, DMSO) δ 10.90 (s, 1 H), 9.03
(s, 1 H), 7.94 – 7.82 (m, 2 H), 7.61 – 7.45 (m, 4 H), 7.32 (ddd, J = 8.7,
7.4, 1.7 Hz, 1 H), 6.94 – 6.79 (m, 2 H). 13C NMR (76 MHz, DMSO) δ
165.79, 164.86, 159.24, 134.05, 132.96, 132.47, 132.42, 129.82,
catalyst) was slowly added to the reaction mixture was then allowed to
stir at 75 ◦C for 5 h. Then it has been cooled at room temperature and
filtered the solid product in the pure form (10). M.p.: 198 ◦C; 1H NMR
(300 MHz, DMSO) δ 12.33 (s, 1 H), 10.62 (s, 1 H), 8.85 – 8.74 (m, 2 H),
8.71 (s, 1 H), 7.92 – 7.84 (m, 2 H), 7.18 (d, J =2.6 Hz, 1 H), 7.01 – 6.80
(m, 2 H), 3.73 (d, J =1.0 Hz, 3 H). 13C NMR (75 MHz, DMSO) δ 161.89,
152.65, 152.12, 150.77, 150.04, 149.03, 140.47, 123.32, 122.00,
127.86, 120.02, 118.21, 116.95, 76.28.; FT-IR (KBr disk): ν 3385, 3050,
2929, 1603, 1466, 1268 cmꢀ 1; MS m/z: 446 (M+). Anal. Calcd. For
C
28H22N4O2: C, 75.32; H, 4.97; N, 12.55; Found: C, 75.50; H, 4.76; N,
119.35, 119.08, 117.82, 112.48, 55.88. FT-IR (KBr disk): ν 3433, 3200,
13.39 %.
3065, 2954, 2839, 1653, 1583, 1494, 1272 cmꢀ 1; MS m/z: 271 (M+).
Anal. Calcd. For C14H13N3O3: C, 61.99; H, 4.83; N, 15.49; Found: C,
62.11; H, 4.91; N, 15.36 %.
2.2.10. 2,2′-(((1E,2E)-ethane-1,2-diylidene)bis(azaneylylidene))
diphenols (L9)
To a stirring solution of Oxalaldehyde (1.14 ml, 10 mmol) in ethanol
(20 mL), 2-Aminophenol (2.18 g, 20 mmol) was added. Then glacial
acetic acid (0.1 mL, as a catalyst) was slowly added to the reaction
mixture was then allowed to stir at 75 ◦C for 5 h. Then it has been cooled
at room temperature and filtered the solid product in the pure form (11).
2.2.8. 2,2′-((1E,1′E)-((1,3phenylenebis(methylene))bis(azaneylylidene))
bis(methaneylylidene)) diphenol (L7)
1
M.p.: 223 ◦C; H NMR (300 MHz, DMSO) δ 7.34 (d, J =4.2 Hz, 1 H),
To a stirring solution of salicylaldehyde (2.44 g, 20 mmol) in ethanol
(20 mL), m-Xylylenediamine (1.36 g, 10 mmol) was added. Then glacial
acetic acid (0.1 mL, as a catalyst) was slowly added to the reaction
mixture was then allowed to stir at 75 ◦C for 6 h. Then it was cooled at
room temperature and filtered the solid product in the pure form (9). M.
p.: 48 ◦C; 1H NMR (300 MHz, DMSO) δ 13.45 (s, 1 H), 8.73 (d, J
=1.3 Hz, 1 H), 7.49 (dd, J = 7.6, 1.8 Hz, 1 H), 7.46 – 7.24 (m, 3 H), 6.99
– 6.86 (m, 2 H), 4.83 (s, 2 H).13C NMR (75 MHz, DMSO) δ 167.07,
161.01, 139.51, 132.92, 132.25, 129.41, 127.75, 127.18, 119.20,
6.71 (dtd, J = 21.5, 14.7, 7.7 Hz, 5 H), 6.54 (s, 2 H), 5.30 (d, J =4.1 Hz,
1 H). 13C NMR (75 MHz, DMSO) δ 141.77, 130.63, 121.86, 119.13,
116.55, 114.67, 75.77. FT-IR (KBr disk):
ν 3383, 3048, 2934, 1609,
1499, 1257 cmꢀ 1; MS m/z: 240 (M+). Anal. Calcd. For C14H12N2O2: C,
69.99; H, 5.03; N, 11.66; Found: C, 69.82; H, 5.11; N, 11.54 %.
2.3. Synthesis of complexes
119.13, 116.95, 62.49. FT-IR (KBr disk):
ν 3423, 3025, 2939, 2898,
2.3.1. General synthesis of complexes
2845, 1608, 1491, 1284 cmꢀ 1; MS m/z: 344 (M+). Anal. Calcd. For
TiCl3 (M1) and TiBr4 (M2) were used as salt metals to be coordinated
by the obtained ligands. Generally, all the complexes were obtained by
the following method:
C
22H20N2O2: C, 76.72; H, 5.85; N, 8.13; Found: C, 76.65; H, 5.68; N, 8.21
%.
Solvents were different according to the salt metals. Methanol was
used for TiCl3 (TiIII), as the solvent, and acetone was used for TiBr4 (TiIV)
complexes. The corresponding ligand was dissolved in the chosen sol-
vent (2 × 10ꢀ 3) and mixed for 30 min, and salt metal was also dissolved
(2 × 10-4) in the same solvent, then it was added drop by drop to the
solution of ligand and it was stirred for 12 h under argon environment.
2.2.9. (E)-N’-(2-hydroxy-5-methoxybenzylidene)isonicotinohydrazide
(L8)
To a stirring solution of 2-Hydroxy-5-methoxybenzaldehyde (1.52 g,
10 mmol) in ethanol (20 mL), 4-pyridinecarboxylic acid hydrazide
(1.37 g, 10 mmol) was added. Then glacial acetic acid (0.1 mL, as a
4

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
There is just a difference between L1, L2, and L3 with other ligands, and it
was usage of NaOH for solving these ligands. Other ligands were dis-
solved just to the solvent.
11.27, Br, 37.61; Found: C, 33.76; H, 3.62; N, 4.33, Ti, 13.27, Br, 35.32
%
After precipitate was appeared, stirring was continued to complete
the reaction, then precipitate was separated from solvent and dried in
the vacuum autoclave at 30℃ for 24 h.
2.3.5. TiIV2(L3)Br4(OH)2, (M2L3), (4)
This complex was prepared in a way similar to that of 1. The colour
changed from pale yellow to red. 1H NMR (300 MHz, DMSO) δ 7.81 (s,
1 H), 6.81 (d, J =15.1 Hz, 2 H), 2.30 (s, 2 H), 2.11 (s, 31 H). 13C NMR
The characterization has been carried out by different methods,
which according to each complex and based on the nature of the com-
plexes, it was different.
(76 MHz, DMSO) δ 207.36, 31.14. FT-IR (KBr disk): ν 3200, 3045, 3025,
2017, 2832, 1623, 1645, 1531, 1489, 1349, 1279 cmꢀ 1. MS m/z: 906
(M+). Anal. Calcd. For C29H22Br4N4O4Ti2: C, 38.45; H, 2.45; N, 6.19, Ti,
10.57, Br, 35.28; Found: C, 38.37; H, 2.66; N, 6.15, Ti, 10.54, Br, 34.28
%.
2.3.2. TiIV(L1)(OH)2H2O, (M2L1), (1)
The procedure was the same as the general method. After adding
TiBr4 solution to the ligand, which was solved in the same solvent
(acetone) and 1 drop NaOH (1 mol), immediately the colour changed
from light red to dark red. The precipitate immediately appeared, and to
complete the reaction it was kept in the reaction solution for 12 h. 1H
NMR (300 MHz, DMSO) δ 12.31 (s, 1 H), 7.91 – 7.75 (m, 3 H), 7.83 (s,
23 H), 7.55 (s, 43 H), 7.51 (s, 3 H), 2.25 – 2.12 (m, 2 H), 2.11 (s, 2 H),
2.10 (s, 18 H), 2.06 (d, J =3.5 Hz, 2 H), 2.08 – 1.93 (m, 2 H), 1.85 (d, J
=1.3 Hz, 2 H), 1.23 (s, 1 H), 1.22 (s, 2 H), 1.16 (s, 2 H). 13C NMR
(76 MHz, DMSO) δ 141.74, 130.59, 121.84, 119.98, 119.10, 116.52,
2.3.6. TiIV(L4)Br2, (M2L4), (5)
This complex was prepared in a way similar to that of 1. However,
NaOH was not used to dissolve the ligand in the solvent. The colour
1
changed from green to orange. H NMR (300 MHz, DMSO) δ 7.84 (s,
7 H), 7.68 (dd, J = 7.7, 1.8 Hz, 1 H), 7.54 (ddd, J = 8.4, 7.2, 1.8 Hz,
2 H), 7.39 (s, 1 H), 7.09 – 6.95 (m, 2 H), 6.97 (s, 2 H), 7.01 – 6.89 (m,
2 H), 3.54 (s, 2 H), 2.84 (d, J =5.9 Hz, 2 H), 2.81 (s, 2 H), 2.11 (s, 37 H),
1.09 (d, J =4.0 Hz, 2 H), 1.02 (d, J =3.6 Hz, 9 H). 13C NMR (76 MHz,
114.65, 75.76, 31.17. FT-IR (KBr disk):
ν
3433, 3200, 3065, 2954, 2839,
DMSO) δ 46.32, 33.20, 31.16, 22.76. FT-IR (KBr disk): ν 2966, 2926,
1653, 1583, 1494, 1272 cmꢀ 1; MS m/z: 271 (M+). Anal. Calcd. For
C14H13N3O3: C, 61.99; H, 4.83; N, 15.49; Found: C, 62.11; H, 4.91; N,
15.36 %.
2806, 2881, 2598, 1656, 1605, 1541, 1261 cmꢀ 1; MS m/z: 516 (M+).
Anal. Calcd. For C19H20Br2N2O2Ti: C, 44.22; H, 3.91; N, 5.43, Ti, 9.28,
Br, 30.97; Found: C, 44.22; H, 3.01; N, 5.65, Ti, 10.12, Br, 29.73 %.
2.3.3. TiIII2(L2)(OH)2, (M1L2), (2)
2.3.7. TiIV(L5)Br2(OH), (M2L5), (6)
The procedure was the same as the general method. After adding
TiCl3 solution to the ligand, which was solved in the same solvent
(methanol) and 1 drop NaOH (1 mol), immediately the colour changed
from orange to red. The precipitate immediately appeared, and to
complete the reaction it was kept in the reaction solution for 12 h. 1H
NMR (300 MHz, DMSO) δ 8.97 (s, 2 H), 7.48 (d, J =2.2 Hz, 2 H), 7.43 (s,
1 H), 7.35 (dd, J = 7.9, 1.6 Hz, 2 H), 7.29 (d, J =2.2 Hz, 1 H), 7.26 (d, J
=2.3 Hz, 1 H), 7.12 (td, J = 7.6, 7.2, 1.6 Hz, 2 H), 7.01 (d, J =8.0 Hz,
This complex was prepared in a way similar to that of 5. The colour
changed from colourless to pale brown. FT-IR (KBr disk):
ν 3395, 2966,
2926, 1656, 1605, 1541, 1261 cmꢀ 1; MS m/z: 555 (M+). Anal. Calcd.
For C20H17Br2N3O3Ti: C, 43.28; H, 3.09; N, 7.57, Ti, 8.62, Br, 28.79;
Found: C, 47.71; H, 3.30; N, 6.53, Ti, 9.22, Br, 27.63 %.
2.3.8. TiIII2(L6)Cl4.9H2O, (M1L6), (7)
The ligand was dissolved (2 × 10ꢀ 3) in a mix of methanol and
ethanol with 80 % and 20 %, respectively. Then TiCl3 with the same
concentration was added and after 30 min, mixing at the room tem-
perature, the temperature was adjusted to 40℃ through the oil bath for
2 h refluxing, the light green colour changed to brown light honey like
colour. After completing the reaction, the precipitate was separated
from the solvent, and then dried in the vacuum autoclave at 30℃ to a
constant mass. 1H NMR (300 MHz, DMSO) δ 10.84 (s, 1 H), 9.01 (s, 1 H),
8.11 – 7.91 (m, 1 H), 7.89 – 7.74 (m, 4 H), 7.71 – 7.61 (m, 1 H), 7.66 –
7.55 (m, 1 H), 7.55 (d, J =4.0 Hz, 4 H), 7.55 – 7.40 (m, 2 H), 7.43 – 7.19
(m, 10 H), 7.19 – 7.10 (m, 3 H), 7.10 – 6.73 (m, 5 H), 6.66 (t, J =7.4 Hz,
1 H), 2.42 (s, 1 H), 2.25 – 1.97 (m, 1 H), 1.75 – 1.28 (m, 2 H), 1.25 (s,
2 H), 1.26 – 1.08 (m, 1 H). 13C NMR (76 MHz, DMSO) δ 164.70, 159.14,
134.07, 132.95, 132.43, 130.67, 130.08, 130.01, 129.84, 128.91,
2 H), 6.96 (s, 2 H), 6.94 – 6.77 (m, 5 H), 3.91 (s, 2 H), 3.83 (s, 0 H). 13
C
NMR (76 MHz, DMSO) δ 161.84, 159.63, 151.89, 135.40, 133.75,
132.28, 132.02, 128.41, 120.16, 119.82, 117.30, 117.11. FT-IR (KBr
disk):
ν
3060, 2900, 2835, 1614, 1597, 1490, 1469, 1281, 1142 cmꢀ 1
.
MS m/z: 563 (M+); Anal. Calcd. For Ti2C27H20N2O6: C, 57.48; H, 3.57; N,
4.97, Ti, 16.97; Found: C, 56.31; H, 3.93; N, 3.70, Ti, 17.03 %.
2.3.4. TiIV2(L2)Br4, (M2L2), (3)
This complex was prepared in a way similar to that of 1. The colour
changed from orange to red. 1H NMR (300 MHz, DMSO) δ 10.58 (d, J
=5.8 Hz, 1 H), 10.39 (s, 5 H), 10.24 (d, J =2.6 Hz, 1 H), 8.12 (d, J
=3.3 Hz, 2 H), 7.72 (s, 1 H), 7.49 (dt, J = 6.5, 2.3 Hz, 1 H), 7.41 (ddd,
J = 10.7, 4.3, 2.4 Hz, 2 H), 7.32 – 7.23 (m, 2 H), 7.26 – 7.19 (m, 1 H),
7.17 (ddd, J = 15.7, 8.1, 2.6 Hz, 1 H), 7.05 (dt, J = 7.8, 1.6 Hz, 1 H),
7.05 – 6.86 (m, 5 H), 6.86 – 6.65 (m, 3 H), 6.16 (d, J =1.3 Hz, 1 H), 3.85
(t, J =5.0 Hz, 2 H), 3.19 (s, 1 H), 2.91 (s, 1 H), 2.75 (s, 1 H), 2.50 (s,
1 H), 2.33 (d, J =10.1 Hz, 1 H), 2.11 (s, 6 H), 2.25 – 2.03 (m, 5 H), 2.03
– 1.90 (m, 2 H), 1.95 – 1.81 (m, 2 H), 1.43 (s, 1 H), 1.41 (s, 1 H), 1.33 (s,
0 H), 1.25 (s, 5 H), 1.16 (s, 4 H), 0.86 (q, J = 7.2, 6.6 Hz, 1 H); 13C NMR
128.81, 128.04, 127.83, 120.07, 118.23, 116.93. FT-IR (KBr disk):
ν
3154, 2921, 1606, 1486, 1272 cm-1. MS m/z: 841 (M+). Anal. Calcd. For
C28H35Cl4N4O11Ti2: C, 39.81; H, 4.50; N, 6.63; Ti, 11.38; Cl, 16.86;
Found: C, 39.70; H, 4.48; N, 6.66;Ti, 12.22; Cl, 15.71 %.
2.3.9. TiIII(L7)OH.4H2O, (M1L7), (8)
(76 MHz, DMSO) δ 18.92, 39.92, 39.65, 39.37, 56.55. FT-IR (KBr disk):
ν
This complex was prepared in a way similar to that of 7. The colour
3064, 2896, 2920, 1612, 1586, 1468, 1282, 1158 cmꢀ 1; MS m/z: 850
changed from light green to yellow. FT-IR (KBr disk): ν 3391, 3020,
(M+). Anal. Calcd. For C27H18Br4N2O4Ti2: C, 38.16; H, 2.14; N, 3.30, Ti,
2948, 1592, 1491, 1311 cmꢀ 1; MS m/z: 540 (M+). Anal. Calcd. For
5

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Fig. 1. Charge of the UV–vis spectra of ethanol solutions of L4 (a), L7 (b), and L8(c) at dropwise addition of a solution of TiCl3 (arrow show the change in absorption).
C24H31N2O6Ti2: C, 53.36; H, 5.97; N, 5.19; Ti, 17.72; Found: C, 55.03; H,
5.72; N, 5.20; Ti, 16.91 %.
changed from orange to dark green. 1H NMR (300 MHz, DMSO) δ 9.93
(s, 2 H), 7.33 (d, J =4.2 Hz, 2 H), 7.00 (d, J =7.6 Hz, 1 H), 6.88 (d, J
=2.4 Hz, 2 H), 6.82 – 6.56 (m, 12 H), 5.27 (d, J =3.9 Hz, 3 H), 3.18 (s,
1 H), 2.10 (s, 23 H), 2.17 – 2.03 (m, 2 H), 1.92 – 1.83 (m, 1 H), 1.25 (s,
1 H), 1.16 (s, 1 H). 13C NMR (76 MHz, DMSO) δ 199.40, 160.31, 145.64,
138.20, 131.38, 129.88, 128.22, 125.85, 124.84, 124.58, 122.67,
2.3.10. (TiIVO)2(L7)Br2, (M2L7), (9)
This complex was prepared in a way similar to that of 1. The colour
1
changed from green to orange. H NMR (301 MHz, DMSO) δ 8.32 (s,
5 H), 7.66 – 7.46 (m, 3 H), 6.88 (s, 3 H), 4.07 (s, 3 H), 2.10 (s, 20 H). 13
C
122.05, 117.43, 31.89, 29.83, 28.02. FT-IR (KBr disk): ν 3398, 3048,
NMR (76 MHz, DMSO) δ 139.06, 134.65, 132.32, 130.00, 129.60,
3219, 1609, 1495, 1266 cmꢀ 1; MS m/z: 528 (M+). Anal. Calcd. For
129.34, 127.05, 116.67, 42.58, 27.87. FT-IR (KBr disk):
ν
3395, 3023,
C14Br2H12N2O4Ti2: C, 31.86; H, 2.29; N, 5.31; Ti, 18.14; Br, 30.28;
2959, 2700, 2602, 1704, 1598, 1500, 1311 cmꢀ 1; MS m/z: 630 (M+).
Anal. Calcd. For C22H18Br2N2O4Ti2: C, 41.95; H, 2.88; N, 4.45; Ti, 15.20;
Br, 25.37; Found: C, 42.97; H, 3.28; N, 5.05; Ti, 15.20; Br, 25.37 Ti,
16.18; Br, 14.23 %.
Found: C, 32.56; H, 3.19; N, 6.37; Ti, 17.12; Br, 31.23 %.
2.4. Typical procedure for C-N cross coupling reaction
The procedure for the C-N cross coupling reaction was the same for
the different heterogeneous photocatalysts. In a typical procedure, to a
stirred mixture of bromobenzene (1 mmol, 0.093 g), aniline derivatives
(1 mmol) and K2CO3 (1 mmol, 0.138 g) in DMF (4 mL), M1L8 (10)
(0.4 mol%, 0.0016 g) was added. The reaction mixture was located
under sunlight irradiation at ambient temperature (a sunny day, in July,
in Mashhad between 10 am to 5 pm at the temperature ranges of 22–34
⁰C). The reaction was monitored by TLC. The reaction mixture colour
changed from yellow to brown. After completion of the reaction, the
catalyst was separated and the desired product was extracted by ethyl
acetate (4 mL). The obtained crude product was purified by thin layer
chromatography using n-hexane/ethyl acetate (50:1).
2.3.11. TiIII(L8)Cl2.H2O, (M1L8), (10)
This complex was prepared in a way similar to that of 2. The colour
changed from pale yellow to red wine. FT-IR (KBr disk):
ν 3329, 3054,
2943, 2832, 1642, 1579, 1508, 1270 cmꢀ 1; MS m/z: 408 (M+). Anal.
Calcd. For C14H16Cl2N3O4Ti: C, 41.11; H, 3.94; N, 10.27; Ti, 11.70; Cl,
17.33; Found: C, 42.56; H, 3.20; N, 8.89; Ti, 10.35; Cl, 16.98 %.
2.3.12. (TiIVO)(L8)Br, (M2L8), (11)
This complex was prepared in a way similar to that of 1. The colour
changed from pale yellow to red. 1H NMR (300 MHz, DMSO) δ 12.45 (s,
1 H), 9.19 (s, 1 H), 9.01 – 8.91 (m, 1 H), 8.86 – 8.78 (m, 2 H), 8.13 –
8.02 (m, 1 H), 8.02 – 7.94 (m, 2 H), 7.49 (d, J =3.2 Hz, 1 H), 7.25 – 7.15
(m, 1 H), 7.01 – 6.81 (m, 1 H), 6.75 (d, J =9.0 Hz, 1 H), 4.51 (s, 12 H),
3.78 (d, J =18.7 Hz, 5 H), 2.10 (s, 1 H). 13C NMR (76 MHz, DMSO) δ
166.15, 161.35, 157.29, 154.25, 153.22, 152.67, 152.00, 149.41,
149.06, 148.82, 147.71, 142.72, 124.88, 124.12, 123.49, 123.08,
3. Results and discussion
3.1. Synthesis and characterization
The organic ligands L1–L9 were isolated and purified using general
procedures of condensation of aldehydes and ketones with amines and
hydrazides. The purity of the basic products was explored by thin layer
chromatography. The mass spectra of the compound contain signals
corresponding to the molecular ion (M+). The IR and NMR spectra
indicated bands and signals of characteristic fragments and functional
groups which will be discussed later.
119.41, 117.89, 116.93, 112.01, 56.29, 55.99. FT-IR (KBr disk): ν 3380,
3047, 3065, 2835, 2574, 1634, 1589, 1559, 1271 cmꢀ 1; MS m/z: 478
(M+). Anal. Calcd. For C14H13BrN3O5Ti2: C, 35.11; H, 2.74; N, 8.77; Ti,
19.99; Br, 16.68; Found: C, 37.56; H, 3.19; N, 8.89; Ti, 21.03; Br, 15.23
%.
2.3.13. (TiIVO)2(L9)Br2, (M2L9), (12)
The ability of L1–L9 to form complexes with TiIII and TiIV species was
This complex was prepared in a way similar to that of 2. The colour
6

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Table 1
Features of the complexes in aqueous solution from analysis of their UV–vis
spectra.
Compounds
n (MLn)
Logβ
Logβ/n
λmax
TiIV(L1)(OH)2⋅H2O
TiIII2(L2)(OH)2
TiIV2(L2)Br4
2
2
2
2
1
1
1
1
1
1
1
1
19.02
15.38
16.20
18.51
17.32
6.84
9.51
265
341
361
266
405
266
303
278
261
283
272
279
7.69
8.1
TiIV2(L3)Br4(OH)2
TiIV(L4)Br2
9.25
17.32
6.84
TiIV(L5)Br2(OH)
TiIII2(L6)Cl4⋅9H2O
TiIII(L7)OH⋅4H2O
(TiIVO)2(L7)Br2
TiIII(L8)Cl2⋅H2O
(TiIVO)(L8)Br
11.43
10.929
9.59
11.43
10.929
9.59
7.94
7.94
10.048
8.20
10.048
8.20
(TiIVO)2(L9)Br2
Fig. 4. XRD pattern of M2Lx.
Table 2
2 θ of the samples obtained from the ligands and complexes.
Compounds
2θ
L1
36.46
TiIV(L1)
31.105
(OH)2⋅H2O
L2
14.385,16.035, 18.385, 21.665, 24.865, 28.395
18.3, 21.3, 21.8, 29.3, 32.1, 35.2, 37.2, 38.3, 45.3, 55.2, 55.6,
59.1, 62.2, 75.1
TiIII2(L2)(OH)2
TiIV2(L3)Br4
L3
–
11.255, 13.735, 17.395, 18.375, 18.815, 20.855, 22.355, 25.545,
26.965, 27.815, 29.015, 31.065, 33.155
25.805, 29.865, 42.725
TiIV2(L3)
Br4(OH)2
L4
11.165, 18.195, 18.865, 19.025, 21.945, 22.025, 22.105, 22.165,
22.665, 23.345, 23.455, 26.395, 28.055, 28.155, 28.205, 28.285
Fig. 2. XRD pattern of the ligands.
TiIV(L4)Br2
L5
22.045, 22.635, 22.925, 24.585, 29.435, 30.075
16.095, 16.795, 17.775, 19.735, 21.475, 22.885, 23.605, 25.205,
27.305, 30.235
TiIV(L5)Br2(OH)
L6
–
16.775, 20.825, 25.085, 25.325
TiIII2(L6)
Cl4⋅9H2O
11.535, 12.745, 18.615, 19.575, 21.025, 22.165, 22.505, 22.715,
23.345, 23.605, 24.005, 24.435, 24.955, 26.105, 27.515, 28.495,
28.725, 31.915, 32.165, 34.185, 38.235, 42.925, 45.545, 46.575,
50.485
L7
14.495, 19.015, 19.815, 24.265
TiIII(L7)
15.225, 22.735, 24.395, 27.305, 28.845, 29.975, 31.215, 34.115,
OH⋅4H2O
(TiIVO)2(L7)Br2
L8
35.715
20.215, 22.165, 23.565, 28.085, 45.355
12.305, 13.625, 15.165, 17.235, 18.315, 20.145, 21.965, 24.145,
24.935, 27.055, 28.305
TiIII(L8)Cl2⋅H2O
(TiIVO)(L8)Br
L9
–
20.4252, 24.6199, 25.7431, 26.9657, 27.9299, 28.6257
12.815, 18.415, 19.435, 20.035, 22.005, 24.265, 25.695, 27.045,
31.405
(TiIVO)2(L9)Br2
–
Fig. 3. XRD pattern of M1Lx.
solutions (see the synthetic part). Table 1 lists the results of UV–vis
spectroscopy for all the complexes.
examined by the UV–vis spectroscopic titration method (Fig. 1). In all
the cases, a redshift was observed in the absorption band of the ligands
upon dropwise addition of Ti salts which is in favor of the synthesis of
catalysts capable of working under visible light. The redshift reflects a
decline in the energy bandgap (Δ = E(HOMO) – E(LUMO)), thus, the
shift of wavelength toward the lower energies (visible light). Therefore,
the obtained catalysts can absorb visible light. The isosbestic points in
the spectra indicate the equilibrium processes of complex formation.
The emergence of longer wavelength absorption bands does not
contradict the formation of deeply colored complexes isolated from
A comparison of the XRD results of L1–L9 with their corresponding
TiIII and TiIV complexes indicated the formation of new phases
(Figs. 2–4). The ligand peaks disappeared or shifted in the complexes.
Thus, no mixtures of Ti-salts with the organic species were isolated. It
must be noted that L1, TiIV2(L2)Br4 (3), TiIV(L5)Br2(OH) (6), and (TiI-
VO)2(L9)Br2 (12) did not give reflections in the XRD patterns, i.e. they
are amorphous. The XRD results of all complexes are presented in
Table 2.
The SEM images of the isolated complexes showed that the majority
of the samples have a proper surface area. As an example, TiIV(L5)
7

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Fig. 5. SEM images of TiIV(L5)Br2(OH) (a–c) and (TiIVO)2(L7)Br2 (d–f) at various magnifications.
Br2(OH) complex exhibited a highly porous sponge-like structure
(Fig. 5) which is attractive for catalytic activities.
3.3. L1 and TiIV-complex
According to the elemental analysis, the composition of the complex
can be presented as TiIV(L1)(OH)2⋅H2O. As NaOH solution was used to
increase the solubility of L1 and acetone used as a solvent, the intro-
duction of OH groups and water molecules into the complex was not
unexpected. The 1H NMR spectrum of the ligand showed a peak at
9.72 ppm which correlates to two protons of the hydroxy groups. No
peak was observed in this area for the Ti-complex which may indicate
the dissociation of the OH-groups of the ligand upon complexation. The
peaks at 2.25–2.12 (m, 2 H) and 2.11 (s, 2 H) ppm can be assigned to the
protons of OH groups and H2O molecule, respectively. The shift in the
3.2. Spectral characteristics and expected structure of the complexes
In all the cases the complexation of Ti with the organic ligands can be
proved by the strong changes in color. In all cases, the shifts are observed
in the absorption bands (the color changes to the orange-reddish part of
the spectrum) which can be attributed to the formation of new unoc-
cupied molecular orbitals involving Ti atomic orbitals. These orbitals
decremented the energy band gap, offering the possibility of visible light
absorption.
–
–
signal of H C N proton at complexation reflects the involvement of N-
–
As the single crystal isolation of the complexes failed, the structures
of the isolated compounds were predicted from their spectroscopic
characteristics.
pyridine in coordination. Thus, the structure of the complex may be
presented as (12):
8

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
3.5. L3 and TiIV-complex
According to the elemental analysis, the composition of the complex
can be presented as TiIV2(L3)Br4(OH)2. In the IR spectrum of L3, the
characteristic absorption band of C O stretching at 1648 cmꢀ 1 did not
–
–
shift upon complexation, indicating that the carbonyl groups of the
organic ligand are not involved in coordination with Ti. The absorptions
at 3205 and 3108 cmꢀ 1 can be assigned to
ν
– –
(N H) and ν(O H),
respectively. The significant low-frequency shift of the OH bands could
be assigned to the strong intramolecular H-interactions with N-atoms of
neighboring hydrazo-groups. In the IR spectrum of the complex, the
–
band assigned to the N H stretches remained unchanged while the
ꢀ 1
–
(O H) absorption bands disappeared. A new broad band at 3460 cm
3.4. L2 and TiIII/TiIV-complexes
ν
in the spectrum of the complex compound indicates the presence of
hydroxy-groups attached to the Ti cations.
According to elemental analysis, the composition of the complex
compounds can be presented as TiIII2(L2)(OH)2 and TiIV2(L2)Br4. The
absorption bands of the OH-groups in the IR spectrum of the ligand are
observed as a wide band of rather low intensity in the range
The 1H spectrum of the L3 ligand contains the signals at 11.08 (2H,
OH) and 12.10 (2H, NH) ppm. The signal at 8.65 ppm (2 H) can be
–
–
–
HC N
–
ascribed to two equivalent independent protons of the
3400–3000 cmꢀ 1 which overlapped with the C H aromatic stretches.
fragments. Upon the complex formation, the signal at 11.08 ppm dis-
–
–
appeared, and the signal of the N H protons emerged at 11.48 ppm
This absorption band disappeared in the IR spectra of the complexes,
indicating the involvement of neighboring N atoms of two hydrazo-
–
indicating the ionization of the OH groups. The ν(C O) band of the
–
–
–
–
frag-
ligand at 1275 cmꢀ 1 shifted to higher frequencies (1282 and 1281 cmꢀ 1
for TiIII and TiIV complexes, respectively), implying a decrease in the
electron density on O-atoms due to their coordination with Ti-ions.
The 1H NMR spectrum of L2 is characterized by two signals at 9.72
(2 H) and 13.62 (2 H) ppm which can be assigned to two pairs of non-
equivalent hydroxy groups. Two of the OH-groups are involved in
strong intramolecular H-bonding, while the other two form the inter-
molecular H-bonds are associated with the organic molecules in the
crystal. No signals were detected above 9 ppm in the 1H NMR spectra of
the complexes indicating the ionization of the OH-groups during the
complexation.
groups in coordination. Together, the signal of the HC
N
ments shifted to 8.51 ppm. The appearance of a signal at 2.10 ppm in the
spectrum of Ti2(L3)Br4(OH)2 can be assigned related to two OH-groups
in the inner sphere of the Ti cations.
Summarizing all the abovementioned discussions and considering
that the coordination numbers of Ti(IV) can be 4, 5, or 6, the following
structure can be proposed (15).
–
–
The position of the C H protons of the C N fragments of the
–
organic species (8.94 ppm, s, 2 H) does not significantly change upon
complexation (8.96 ppm). One can suppose that the N-atoms of the L2
molecule were not involved in coordination. Based on the coordination
number of Ti as 4 and the geometrical features of the organic molecule,
two structures (TiIII2(L2)(OH)2 and TiIV2(L2)Br4) can be proposed as
binuclear monomeric (13a, 13b) or coordination polymer (14b, 14b) in
which two of the O-atoms of the terminal fragments of L2 form coordi-
nate bonds with the Ti atoms of the neighboring monomers.
3.6. L4 and TiIV-complex
The elemental analysis indicates that the Ti-to-L4 ratio in the com-
plex is ranged from 1 to -1. The formula can be presented as TiIV(L4)Br2.
No characteristic absorption bands can be observed in the IR spectra of
both L4 and its Ti complex. In the 1H NMR spectrum of the organic
species, two protons of the OH groups (13.60 ppm) and two protons of
9

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Table 3
Selected calculated parameters for L1 – L9.
Compound
E(HOMO), eV
E(LUMO), eV
ΔE, eV
Dipole moment, Debye
L1
L2
L3
L4
L5
L6
L7
L8
L9
ꢀ 8,2353
ꢀ 8,2016
ꢀ 8,1781
ꢀ 8,4374
ꢀ 9,2868
ꢀ 7,9075
ꢀ 8,5569
ꢀ 7,9459
ꢀ 7,9717
ꢀ 0,9745
ꢀ 0,3371
0,1732
7,2608
7,8645
8,3513
8,7836
9,6112
7,7187
9,1873
7,6056
7,6747
4,63
3,49
2,32
4,46
5,46
1,59
3,32
4,78
0,08
0,3462
0,3244
ꢀ 0,1888
0,6304
ꢀ 0,3403
ꢀ 0,2970
Scheme 1. Formation of titanyl ions at complex formation.
–
–
–
fragments (8.38 ppm) can be observed. In the spectrum
the HC
N
–
of Ti(L4)Br2, the signal of OH groups is not observed, and the signal of
–
–
–
fragments shifted to 8.21 ppm indicating the involvement of
HC
N
–
N-atoms in coordination with titanium. The proposed structure of the
complex compound is presented below (16):
3.9. L7 and TiIII/ TiIV complexes
Determination of the molecular structure of complexes in the
absence of a single crystal was done by DFT optimizations in the gas
phase of the ligands (Fig. 4). Selected energetic and geometrical pa-
rameters of L1 – L9 are presented in Table 3.
Ti(IV) atom is six coordinated and forms a distorted octahedral co-
ordination sphere where two Br atoms act as azimuthal ligands.
3.7. L5 and its TiIV complex
The composition of the Ti-complex compound of L5 is Ti(L5)Br2(OH);
implying the existence of organic ligand in the form of mono-anion.
Comparison of the IR spectra of L5 and its complex indicated no shift
of the absorption band of the C O group (1676 cmꢀ 1 in L5 vs 1680 cm-1
–
–
IV
5
–
in Ti (L )Br (OH)). Thus, the C O group is not involved in coordina-
–
2
tion. The structure of the complex compound can be presented as:
According to the elemental analysis, the composition of the complex
compound of TiIV with L7 is related to the formula (TiIVO)2(L7)Br2. The
presence of the titanyl fragment (TiO)2+ can be predicted using IR
ꢀ 1
–
spectra. New adsorption bands at 900 (
ν
(Ti O)) and 660/625 cm
(ν
–
–
(Ti O)) appear in the spectrum of the complex compared to that of the
ligand. The formation of titanyl ions upon complexation is in accordance
follows the scheme of the hydrolysis of Ti(IV) ions proposed by Comba &
Metbach (Scheme 1) [84]:
The dissociation of the two hydroxy-groups of L7 upon complexation
is manifested as the signals of two protons at 13.45 ppm on the 1H NMR
spectrum of the ligand which is not observable in the case of (TiIVO)2(L7)
The N-atom of the pyridine fragment of the organic ligand may form
an additional coordination bond with a Ti atom of a neighboring
molecule; resulting in the formation of a polymeric structure.
–
–
–
–
fragment in the organic
Br2. The signal of two protons of the HC
N
species at 8.73 ppm (2 H) shifted to 8.32 ppm(5 H) upon complexation
and overlapped with the signals of the protons of benzene rings of the
organic molecule, indicating the involvement of N-lone electron pairs in
coordination with Ti(IV). As a result, the structure of the complex
compound can be presented as (20):
3.8. L6 and its Ti complex
TiIII2(L6)Cl4⋅9H2O is the formula of the complex derived from the
elemental analysis. Nine lattice water molecules indicate strong hygro-
scopic properties of the substance. In the IR spectrum of the complex,
their vibration appeared as a wide strong absorption in 3380-3200 cmꢀ 1
which overlapped with the area of OH stretchings of L6 (3250 cmꢀ 1).
However, the absence of the signals of protons at 10.90 (s, 1H, OH) and
9.03 (s, 1H, OH) ppm in the spectrum of TiIII2(L6)Cl4⋅9H2O showed the
ionization of the ligand upon complexation. The structure of coordina-
tion of L6 in the TiIII complex can be presented as (18):
10

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Fig. 6. DFT optimized structures of L1 – L9.
3.10. L8 and TiIII/ TiIV complexes
In the IR spectrum of the ligand,
a board absorption at
3434ꢀ 3300 cmꢀ 1
– –
(ν(O H + N H)) got sharper upon complexation
with a maximum at 3329 and 3380 cmꢀ 1
III
8
–
(ν(N H)) for Ti (L )Cl2⋅H2O
and (TiIVO)(L8)Br, respectively. This may due to the ionization of hy-
1
droxy groups. A comparison of the H NMR spectra of the complexes
with the free (non-complexed) ligand showed that the signal of two
protons of the hydroxy-groups (at 10.62 ppm) disappeared while the
signal of the protons of the NH-groups at 12.33 ppm was observed in
both spectra.
–
–
The absorption band of the C O group in the IR spectrum of the
ligand (1653 cmꢀ 1) shifted to a lower frequency (1635 and 1642 cmꢀ 1
for TiIII(L8)Cl2⋅H2O and (TiIVO)(L8)Br) upon complexation, indicating
the formation of a coordinate bond with the TiIII and TiIV cations. The
formation of a titanyl fragment (TiO)2+ in the complex of TiIV can be
inferred by the emergence of a new adsorption band at 914 cmꢀ 1
(ν
–
(Ti O)).
–
Based on the spectral characteristics of the complex compared with
the uncoordinated L8, two possible types of coordination can be
proposed.
3.11. L9 and TiIV complex
In the first type, L8 acts as a tridental ligand to form monomeric
mononuclear complexes of 21a and 22a. In the second case, L8 serves as
According to the elemental analysis, the formula of the complex
–
–
compound is (TiIVO)2(L9)Br2. In the IR spectrum of the ligand, a broad
a tridental bridging ligand where the C O group of one ligand molecule
absorption is observed with a maximum at 3384 cmꢀ 1
(
ν
(O H)). In the
forms a coordinate bond with a Ti atom of a neighboring monomer. The
N-pyridine atom can be also involved in coordination, giving rise to 3D
polymeric structures (21b and 22b). Thus, the structures of the complex
may be presented as:
–
spectrum of the complex, no band was observed in this region, implying
the dissociation of OH groups of the ligand. The titanyl group vibrations
in the IR spectrum of the complex corresponded to 902 cmꢀ 1
.
The 1H NMR spectrum of the ligand shows the signal of two protons
of hydroxy groups at 9.93 ppm which disappeared upon complexation.
The proposed structure of the complex can be presented as following
(23):
11

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
involving only O-atoms (Table 4).
DFT optimization of the (TiIVO)2(L7)Br2 structure is presented in
Fig. 8. The TiIV O bond length was determined as 1.6 Å reflecting its
–
–
double character. The IR spectrum simulation resulted in 994 cmꢀ 1 and
626 cmꢀ 1 for (
ν
–
–
(Ti O) and (ν(Ti O), respectively which well coin-
–
cided with the experimental IR spectrum of (TiIVO)2(L7)Br2 (Fig. 9). The
spectrum of the complex showed absorption peaks at 900 and 660/
625 cmꢀ 1 which are not observed in the spectrum of L7.
4. Photocatalytic activity of complexes as catalysts in the C–N
cross-coupling reaction
To evaluate the photocatalytic efficiency of the obtained complexes,
they were used in the C-N cross-coupling. The catalytic activity of the
complexes was investigated in the Buchwald-Hartwig reaction. For this
purpose, the cross-coupling reaction between bromobenzene and aniline
was considered as a model reaction. To better estimate the reaction
condition, the effects of the different parameters such as solvent, base,
the molar ratio of bromobenzene, base, and catalyst were first examined.
The data corresponding to TiIII(L8)Cl2.H2O (M1L8) can be found in
Table 5. The photocatalytic activity and reaction conditions are sum-
marized in Table 5.
Fig. 7. Molecular electrostatic potential (MESP) of L1.
According to the result, the reaction did not occur in the absence of a
catalyst or base for any types of catalysts. These results confirmed the
photocatalytic nature of the complexes showing the necessity of both
base and catalyst for the C-N cross-coupling reaction (Table 5, entries
1–3). In the second screening experiment, the effects of various solvent
systems were investigated. For this purpose, different polar/non-polar
solvents (such as DMSO, DMF, THF, DCM, toluene, CH3CN, EtOH,
3.12. Theoretical simulations
The molecular structure of complexes was determined by DFT opti-
mizations in the gas phase of the ligands (Fig. 6). The energetic and
geometrical parameters of L1–L9 are presented in Table 3
Molecular electrostatic surface potential (MESP) charge regionali-
zation was set up by electron density plot. As an example, the MESP
potential of L1 is presented in Fig. 7 which indicates that the O atoms of
hydroxy groups possess a negative potential region, i.e. are the most
preferable coordination sites of the ligand. Similar results were reported
by Shukla et al. for the Schiff base complexes of titanocene dichloride
[85].
The spatial arrangement of the electron-donating fragments of the
molecules (L1 – L9) is in line with the proposed structures of the com-
plexes derived from the spectral studies. For example, in the case of Ti-
complexes with L2, phenolic groups of neighboring phenolic fragments
are in the sin-position. Thus, monomeric binuclear complexes of 13a and
14a seem to be more preferable than polymeric 13b and 14b structures.
The complexes with bis(tridentate) coordination of L2 via two oxygens
–
–
–
–
N fragment
of deprotonated OH groups and an N atom of the HC
Fig. 8. DFT optimization of (TiIVO)2(L7)Br2.
are in lower energy levels compared to bis(bidentate) coordination
Table 4
Relative energies of bis(bidentate) and bis(tridentate) coordination of L2 (only one coordination fragment is considered for clarity).
ΔE, kJ/mol
0
86.62
12

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Fig. 9. IR spectrum of (TiIVO)2(L7)Br2 (a); calculated for (TiIVO)2(L7)Br2 (b).
Table 5
Optimization of the reaction conditions for coupling reaction.
Entry
Catalyst (mol%)e
Base
Solvent
Molar ratio of Bromobenzene/Base
Time (h)
Isolated Yield (%)a,b
1
–
–
–
DMF
1/0
1/1
1/0
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/2
1/0.5
1/1
1/1
1/1
1/1
24
24
24
24
4
0a
2
K2CO3
–
DMF
0a
3
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.2
0.6
0.4
0.4
DMF
0a
4
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
KOH
DMF
0b
5
DMF
84a
84a
40a
45a
Tracea
23a
35a
45a
65a
60a
30a
75a
75a
68a
45a
40a
84a
60a
67a
80a
84c
84d
6
DMSO
EtOH
EtOH-DMF(9:1)
H2O
4
7
10
8
8
9
24
24
10
6
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
EtOH-H2O(9:1)
THF
DCM
CH3CN
MeOH
Toluene
DMF
6
8
10
5
NaOH
NEt3
DMF
5
DMF
6
K3PO4
NaHCO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
DMF
8
DMF
8
DMF
4
DMF
5
DMF
6
DMF
4
DMF
4
DMF
4
a
b
c
Under sunlight irradiation.
In the dark.
Under 30 W LED irradiation.
Under UV irradiation.
d
e
With respect to bromobenzene.
EtOH-DMF, EtOH-H2O, MeOH, and H2O) were studied (Table 5, entries
5–15). Among the examined solvents, DMF was the best medium with
the highest diphenylamine yield (84 %), thus, it was considered for other
catalysts. H2O resulted in the lowest yield of diphenylamine (Table 5,
entries 5 and 9). Further control experiments were performed regarding
the role of bases on the yield of the C-N cross-coupling reaction.
Therefore, the model reaction was carried out considering different
bases, including K2CO3, KOH, NaOH, NEt3, K3PO4, and NaHCO3,
(Table 5, entries 5, 16–20). It was found that K2CO3 led to a higher yield
(Table 5, entry 5). Then, the amount of base was also explored. Based on
these results, using 1 equivalent of base proceeded the cross-coupling
reaction very effectively (Table 5, entries 5, 21, and 22). There were
no differences in the yield and reaction time between 1 and 2 equiva-
lents of K2CO3. While a decline in the amount of base decremented the
yield of the desired product and prolonged the reaction time (Table 5,
entry 22). The photocatalyst amount was also optimized. The best per-
formance was achieved by applying 0.0016ꢀ 0.0024 g of the catalysts.
As the final control reaction, it was verified that when the reaction was
performed in the dark no catalytic reaction was detected (Table 5, entry
4).
To confirm the excellent sunlight applicability of the photocatalyst,
the optimized reaction condition was tested using different light sources
including blue 30 W LED lamp, 100 W Hg lamp (UVA, UVB Light), and
natural sunlight (Table 5, entry 5, 25, and 26). As shown in Table 5, blue
13

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Table 6
Scope of the C-N cross coupling reaction.
Entry
1
Catalyst
M2L1
R
Product
Time
(h)
Isolated
Yield (%)
4
6
6
84
72
78
2
3
M1L2
M2L2
4
M2L3
7
65
5
6
M2L4
M2L5
4
8
84
65
7
8
9
M1L6
M1L7
M2L7
5
8
5
84
58
79
Scheme 2. Mechanism for M1L8 catalysed C-N cross coupling reaction.
5. Proposed mechanism
Based on some previous reports [86–88], a proposed mechanism was
proposed for catalyzing the C-N cross-coupling reaction (Scheme 2).
Initially, under visible-light irradiation, electrons and holes of TiO2 were
separated and photo-generated electrons migrated. The catalytic cycle
began with the insertion of L8Ti0 into the phenyl–Br bond, yielding to
intermediate B. In the following, coordination of an amine group under
basic condition resulted in intermediate D. The final product and the
reduced form of the catalyst were finally formed in a reductive elimi-
nation step.
10
11
12
M1L8
M2L8
M2L9
8
3
4
50
75
81
6. Conclusion
Reaction conditions: bromobenzane(1.0 mmol), Amine derivatives (1.0 mmol),
K2CO3 (1 mmol), DMF (4.0 mL), Catalyst (0.0016 g) under sunlight at ambient
temperature.
Nine novel Schiff bases were derived from salicylic aldehyde and
oxalic aldehyde in this study. The isolated organic species were
described by a set of experimental methods (IR, CNMR, HNMR, CHN,
SEM, XRD). The molecular structure was also elucidated by DFT opti-
mizations in the gas phase. The molecular electrostatic surface potential
(MESP) charge regionalization was set up by electron density plot. The
redistribution of the electron density in the organic species indicated
their high potential in metal cations chelating with the preferable co-
ordination through O-atoms of the hydroxy-groups of the molecules.
The isolated organic species were applied as the ligands in the re-
action of complex formation with titanium (III) chloride and (IV) bro-
mide. 12 novel complexes were precipitated and studied experimentally
and theoretically. The solution stability of the complexes was indicated
with UV–vis spectroscopic analysis, their formation constants were
calculated to be in the range of 6.84–17.32 depending on the nature of
the Shiff base ligand. Using the DFT def2-TZVP theoretical method
together with the experimental spectroscopic data, the coordination
types of the ligands were detected, and the structure of the complexes
was proposed. The spatial arrangement of the electron-donating frag-
ments of L1 – L9 molecules was in roper accordance with the proposed
structures of the complexes derived from the spectral studies.
30 W LED, Hg lamp, and sunlight showed the same results, so visible
sunlight was chosen for further investigations. Finally, the C-N cross-
coupling reaction was studied using all the catalysts on a sunny day,
in July, in Mashhad between 10 am to 5 pm at the temperature ranges of
22–34 ⁰C.
Almost all the complexes showed their best activity in the same
conditions, so to evaluate the generality and substrate role, the photo-
catalytic activity was further explored under optimized reaction condi-
tion considering C-N cross-coupling reaction with a variety substituted
aromatic amines using K2CO3 as a base in DMF at room temperature
under natural sunlight (Table 6). As shown in Table 6, the reaction
efficiently proceeded with a wide range of electron-withdrawing and
electron-donating substituents. The results showed that both electron-
withdrawing (Table 6, entry 1–8,11) and donating group (Table 6,
entry 9 and 12) were delivered to the corresponding secondary aromatic
amines at moderate to good yields (50–84 %). Comparatively, as ex-
pected, aryl-bearing electron-withdrawing groups reacted significantly
faster than those containing electron-donating groups. Furthermore,
owing to the high steric hindrance of the ortho position, substituents in
the ortho position of amines show low reactivity as compared to the para
one (Table 6, entry 5 and 6). It is worth noting that different catalysts
were applied for different reactions to test different reactions.
The isolated Ti-complexes were used in photocatalytic activity in
Buchwald–Hartwig amination reactions which showed highly efficient
photocatalysis by promoting the C-N cross-coupling reactions using a
wide variety of aromatic and benzylic amines to give cross-coupled
products at proper yields.
The photocatalytic activity of the isolated complexes was checked in
14

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
[6] D.S. Surry, S.L. Buchwald, Dialkylbiaryl phosphines in Pd-catalyzed amination: a
user’s guide, Chem. Sci. 2 (2011) 27–50, https://doi.org/10.1039/c0sc00331j.
[7] J.F. Hartwig, Approaches to catalyst discovery. New carbon-heteroatom and
carbon-carbon bond formation, Pure Appl. Chem. 71 (1999) 1417–1423, https://
doi.org/10.1351/pac199971081417.
the C-N cross-coupling reaction under sunlight using different polar/
non-polar solvents. The studied complexes exhibited high visible-light
photocatalytic activity for a wide range of aromatic and benzylic
amines including electron-withdrawing and electron-donating groups
offering moderate to good yields (50–85 %). Using an inexpensive,
clean, and renewable energy source (sunlight) is the superiority of the
developed photocatalytic systems.
[8] D. Maiti, B.P. Fors, J.L. Henderson, Y. Nakamura, S.L. Buchwald, Palladium-
catalyzed coupling of functionalized primary and secondary amines with aryl and
heteroaryl halides: two ligands suffice in most cases, Chem. Sci. 2 (2011) 57–68,
https://doi.org/10.1039/c0sc00330a.
[9] J.F. Hartwig, Evolution of a fourth generation catalyst for the amination and
thioetherification of aryl halides, Acc. Chem. Res. 41 (2008) 1534–1544, https://
doi.org/10.1021/ar800098p.
The present study offers a promising strategy to design new metal
complexes applicable in various photocatalytic organic reactions.
[10] J.P. Wolfe, S. Wagaw, J.F. Marcoux, S.L. Buchwald, Rational development of
practical catalysts for aromatic carbon-nitrogen bond formation, Acc. Chem. Res.
31 (1998) 805–818, https://doi.org/10.1021/ar9600650.
Authorship contributions
[11] J.F. Hartwig, Transition metal catalyzed synthesis of arylamines and aryl ethers
from aryl halides and triflates: scope and mechanism, Angew. Chemie Int. Ed. 37
(1998) 2046–2067, https://doi.org/10.1002/(SICI)1521-3773(19980817)37:
15<2046::AID-ANIE2046>3.0.CO;2-L.
Conception and design of study: Yahya Absalan, Nazanin Noroozi
Shad, Mostafa Gholizadeh
Acquisition of data: Yahya Absalan, Ghodrat Mahmoudi
Analysis and/or interpretation of data: Yahya Absalan, Pavel
Strashnov, Nazanin Noroozi Shad, Olga Kovalchukova, Hossein Sabet
Sarvestani
[12] D.S. Surry, S.L. Buchwald, Biaryl phosphane ligands in palladium-catalyzed
amination, Angew. Chemie - Int. Ed. 47 (2008) 6338–6361, https://doi.org/
10.1002/anie.200800497.
´
´
´
[13] J.J. Carbo, D. García-Lopez, O. Gonzalez-Del Moral, A. Martín, M. Mena,
C. Santamaría, Carbon-nitrogen bond construction and carbon-oxygen double bond
cleavage on a molecular titanium oxonitride: a combined experimental and
computational study, Inorg. Chem. 54 (2015) 9401–9412, https://doi.org/
10.1021/acs.inorgchem.5b00943.
Drafting the manuscript: Yahya Absalan, Olga Kovalchukova, Naz-
anin Noroozi Shad
Revising the manuscript critically for important intellectual content:
Khashayar Ghandi
[14] C. Paparizos, J.P. Fackler, Kinetic studies by NMR of carbon-nitrogen and carbon-
oxygen bond rotations in dithiocarbamate and aryl xanthate complexes of
dimethylgold(III), Inorg. Chem. 19 (1980) 2886–2889, https://doi.org/10.1021/
ic50212a007.
Approval of the version of the manuscript to be published: Yahya
Absalan, Nazanin Noroozi Shad, Mostafa Gholizadeh, Ghodrat Mah-
moudi, Hossein Sabet Sarvestani, Pavel Strashnov, Khashayar Ghandi,
Olga Kovalchukova.
[15] J.S. Carey, D. Laffan, C. Thomson, M.T. Williams, Analysis of the reactions used for
the preparation of drug candidate molecules, Org. Biomol. Chem. 4 (2006)
2337–2347, https://doi.org/10.1039/b602413k.
[16] C. Torborg, M. Beller, Recent applications of palladium-catalyzed coupling
reactions in the pharmaceutical, agrochemical, and fine chemical industries, Adv.
Synth. Catal. 351 (2009) 3027–3043, https://doi.org/10.1002/adsc.200900587.
[17] W.S. Lo, W.M. Kwok, G.L. Law, C.T. Yeung, C.T.L. Chan, H.L. Yeung, H.K. Kong, C.
H. Chen, M.B. Murphy, K.L. Wong, W.T. Wong, Impressive europium red emission
induced by two-photon excitation for biological applications, Inorg. Chem. 50
(2011) 5309–5311, https://doi.org/10.1021/ic102465j.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper
[18] P. Roy, K. Dhara, M. Manassero, J. Ratha, P. Banerjee, Selective fluorescence zinc
ion sensing and binding behavior of 4-methyl-2,6-bis(((phenylmethyl)imino)
methyl)phenol: biological application, Inorg. Chem. 46 (2007) 6405–6412,
https://doi.org/10.1021/ic700420w.
Acknowledgement
[19] J. Song, T. Jiang, T. Guo, L. Liu, H. Wang, T. Xia, W. Zhang, X. Ye, M. Yang, L. Zhu,
R. Xia, X. Xu, Facile synthesis of water-soluble Zn-doped AgIn5S8/ZnS core/shell
fluorescent nanocrystals and their biological application, Inorg. Chem. 54 (2015)
1627–1633, https://doi.org/10.1021/ic502600u.
This paper has been supported by the RUDN University Strategic
Academic Leadership Program and the Ferdowsi University of Mashhad
research Council
[20] J. Xie, S. Cao, D. Good, M. Wei, X. Ren, Combination of a fluorescent dye and a Zn-
S cluster and its biological application as a stain for bacteria, Inorg. Chem. 49
(2010) 1319–1321, https://doi.org/10.1021/ic9023629.
[21] D.A. Horton, G.T. Bourne, M.L. Smythe, The combinatorial synthesis of bicyclic
privileged structures or privileged substructures, Chem. Rev. 103 (2003) 893–930,
https://doi.org/10.1021/cr020033s.
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jphotochem.2021.
113346.
[22] J.A. Bikker, N. Brooijmans, A. Wissner, T.S. Mansour, Kinase domain mutations in
cancer: implications for small molecule drug design strategies, J. Med. Chem. 52
(2009) 1493–1509, https://doi.org/10.1021/jm8010542.
´
[23] A. Quintas-Cardama, H. Kantarjian, J. Cortes, Flying under the radar: the new wave
of BCR-ABL inhibitors, Nat. Rev. Drug Discov. 6 (2007) 834–848, https://doi.org/
10.1038/nrd2324.
References
[24] S.J. Brickner, D.K. Hutchinson, M.R. Barbachyn, P.R. Manninen, D.A. Ulanowicz, S.
A. Garmon, K.C. Grega, S.K. Hendges, D.S. Toops, C.W. Ford, G.E. Zurenko,
Synthesis and antibacterial activity of U-100592 and U-100766, two oxazolidinone
antibacterial agents for the potential treatment of multidrug-resistant gram-
positive bacterial infections, J. Med. Chem. 39 (1996) 673–679, https://doi.org/
10.1021/jm9509556.
´
[1] P.A. Forero-Cortes, A.M. Haydl, The 25th anniversary of the Buchwald-Hartwig
amination: development, applications, and outlook, Org. Process Res. Dev. 23
(2019) 1478–1483, https://doi.org/10.1021/acs.oprd.9b00161.
[2] A.J. Kendall, L.N. Zakharov, D.R. Tyler, Steric and electronic influences of
Buchwald-type alkyl-JohnPhos ligands, Inorg. Chem. 55 (2016) 3079–3090,
https://doi.org/10.1021/acs.inorgchem.5b02996.
¨
[25] J.W. Nilsson, F. Thorstensson, I. Kvarnstrom, T. Oprea, B. Samuelsson, I. Nilsson,
Solid-phase synthesis of libraries generated from a 4-phenyl-2-carboxy-piperazine
scaffold, J. Comb. Chem. 3 (2001) 546–553, https://doi.org/10.1021/cc010013o.
[26] A.Ç. Atesin, S.B. Duckett, C. Flaschenriem, W.W. Brennessel, R. Eisenberg,
Diastereoselective oxidative addition of dihydrogen to IrI(CO)((R)-BINAP) and [Ir
(CO)2((R)-BINAP)][SbF6], Inorg. Chem. 46 (2007) 1196–1204, https://doi.org/
10.1021/ic061471a.
[3] W.W. Weare, R.R. Schrock, A.S. Hock, P. Müller, Synthesis of molybdenum
complexes that contain “hybrid” triamidoamine ligands, [(hexaisopropylterphenyl-
NCH2CH 2)2NCH2CH2N-aryl]3-, and studies relevant to catalytic reduction of
dinitrogen, Inorg. Chem. 45 (2006) 9185–9196, https://doi.org/10.1021/
ic0613457.
[4] H. Hu, M. Vasiliu, T.H. Stein, F. Qu, D.L. Gerlach, D.A. Dixon, K.H. Shaughnessy,
Synthesis, structural characterization, and coordination chemistry of
(Trineopentylphosphine)palladium(aryl)bromide dimer complexes ([(Np3P)Pd(Ar)
Br]2), Inorg. Chem. 58 (2019) 13299–13313, https://doi.org/10.1021/acs.
inorgchem.9b02164.
[27] Z. Abedin-Siddique, T. Ohno, K. Nozaki, T. Tsubomura, Intense fluorescence of
metal-to-ligand charge transfer in [Pt(0)(binap)2] [binap = 2,2′-Bis
(diphenylphosphino)-1,1′ -binaphthyl], Inorg. Chem. 43 (2004) 663–673, https://
doi.org/10.1021/ic034527z.
[28] T.J. Geldbach, F. Breher, V. Gramlich, P.G.A. Kumar, P.S. Pregosin, X-ray
diffraction and NMR studies on a series of binap-based Ru(II) hydroxyphosphine
[5] Fluorine in Organic Chemistry - Richard D. Chambers - Google Books, (2004).
https://books.google.com/books?hl=en&lr=&id=XE5VHh7uL_
0C&oi=fnd&pg=PR15&dq=R.+D.+Chambers,+Fluorine+in+organic+chemistry.
+CRC+Press:+2004.+b)+P.+Kirsch,+Modern+Fluoroorganic+Chemistry:+
Synthesis,+Reactivity,+Applications+Wiley.+VCH:+2004.+c)+K.+Mu¨ller,+C.+
Faeh,+F.+Diederich,+Fluorine+in+pharmaceuticals:+looking+beyond+
intuition&ots=62yTaXRSPQ&sig=NScwLwR_
π
-Arene complexes, Inorg. Chem. 43 (2004) 1920–1928, https://doi.org/10.1021/
ic0352147.
[29] T. Ohta, H. Takaya, R. Noyori, BINAP-ruthenium(II) dicarboxylate complexes: new,
highly efficient catalysts for asymmetric hydrogenations, Inorg. Chem. 27 (1988)
566–569, https://doi.org/10.1021/ic00276a025.
ym1F9SHrybxE5jEQUcg#v=onepage&q&f=false (accessed June 26, 2020).
15

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
[30] U. Casellato, B. Corain, B. Longato, R. Graziani, G. Pilloni, Heteropolymetallic
complexes of 1,1′-Bis(diphenylphosphino)ferrocene (dppf). 5. Synthesis and
characterization of the cationic complexes [M(dppf)2]+ (M = Rh, Ir). Crystal and
molecular structure of [Ir(dppf)2]B(C6H5)4, Inorg. Chem. 29 (1990) 1193–1198,
https://doi.org/10.1021/ic00331a017.
[52] W.S. Mialki, R.E. Wild, R.A. Walton, Seven-coordinate alkyl isocyanide and mixed-
alkyl isocyanide-phosphine complexes of tungsten(II), Inorg. Chem. 20 (1981)
1380–1384, https://doi.org/10.1021/ic50219a010.
[53] D. Christendat, R.D. Markwell, D.F.R. Gilson, I.S. Butler, J.D. Cotton, Quadrupole-
dipole effects in solid-state phosphorus-315 CP-MAS NMR spectra of tertiary
phosphine substituted alkyl- and acyltetracarbonylmanganese(I) complexes, Inorg.
Chem. 36 (1997) 230–235, https://doi.org/10.1021/ic960476c.
[31] B. Longato, L. Riello, G. Bandoli, G. Pilloni, Iridium(III, 0, and ꢀ I) complexes
stabilized by 1,1‘-Bis(diphenylphosphino)ferrocene (dppf): synthesis and
characterization. crystal structures of [Na(THF) 5][Ir(dppf) 2]⋅THF and [Ir(dppf)
2], Inorg. Chem. 38 (1999) 2818–2823, https://doi.org/10.1021/ic981166s.
[32] F. Canales, M.C. Gimeno, P.G. Jones, A. Laguna, C. Sarroca, Substitution reaction
[54] R.B. King, J.A. Zinich, J.C. Cloyd, Poly (tertiary phosphines and arsines). XII. Some
metal complexes of methylated di- and tri(tertiary phosphines), Inorg. Chem. 14
(1975) 1554–1559, https://doi.org/10.1021/ic50149a022.
studies on [Au 2 Cl 2 (
μ
-dppf)] (dppf = 1,1‘-Bis(diphenylphosphino)ferrocene).
[55] X. Liu, N. Thirupathi, I.A. Guzei, J.G. Verkade, An investigation of staudinger
reactions involving cis-1,3,5- triazidocyclohexane and tri(alkylamino)phosphines,
Inorg. Chem. 43 (2004) 7431–7440, https://doi.org/10.1021/ic0492845.
[56] N. Marion, S.P. Nolan, Well-defined N-heterocyclic carbenes-palladium(II)
precatalysts for cross-coupling reactions, Acc. Chem. Res. 41 (2008) 1440–1449,
https://doi.org/10.1021/ar800020y.
Synthesis of the first gold(I) complex with a
μ
3-2-pyridinethiolate ligand, Inorg.
Chem. 36 (1997) 5206–5211, https://doi.org/10.1021/ic9704445.
[33] M.C. Gimeno, A. Laguna, C. Sarroca, P.G. Jones, 1,1′-Bis(diphenylphosphino)
ferrocene (dppf) complexes of gold(I) and gold(III). Crystal structures of [(dppf)
AuPPh3]ClO4⋅CHCl3 and [(dppf)Au(μ-dppf)Au(dppf)](ClO4)2⋅2CH2Cl2, Inorg.
Chem. 32 (1993) 5926–5932, https://doi.org/10.1021/ic00078a007.
[34] G. Pilloni, A. Toffoletti, G. Bandoli, B. Longato, Homoleptic complexes of cobalt(0)
and nickel(0,I) with 1,1′- bis(diphenylphosphino)ferrocene (dppf): synthesis and
characterization, Inorg. Chem. 45 (2006) 10321–10328, https://doi.org/10.1021/
ic061185z.
[57] M.M. Heravi, Z. Kheilkordi, V. Zadsirjan, M. Heydari, M. Malmir, Buchwald-
Hartwig reaction: an overview, J. Organomet. Chem. 861 (2018) 17–104, https://
doi.org/10.1016/j.jorganchem.2018.02.023.
[58] F. Rataboul, A. Zapf, R. Jackstell, S. Harkal, T. Riermeier, A. Monsees,
U. Dingerdissen, M. Beller, New ligands for a general palladium-catalyzed
amination of aryl and heteroaryl chlorides, Chem. - A Eur. J. 10 (2004) 2983–2990,
https://doi.org/10.1002/chem.200306026.
´
´
[35] M.A. Esteruelas, M. Olivan, A. Velez, Xantphos-type complexes of group 9:
rhodium versus iridium, Inorg. Chem. 52 (2013) 5339–5349, https://doi.org/
10.1021/ic4002658.
[59] Q. Dai, W. Gao, D. Liu, L.M. Kapes, X. Zhang, Triazole-based monophosphine
ligands for palladium-catalyzed cross-coupling reactions of aryl chlorides, J. Org.
Chem. 71 (2006) 3928–3934, https://doi.org/10.1021/jo060321e.
´
[36] A. Escalle, G. Mora, F. Gagosz, N. Mezailles, X.F. Le Goff, Y. Jean, P. Le Floch,
Cationic dimetallic gold hydride complex stabilized by a xantphos-phosphole
ligand: synthesis, X-ray crystal structure, and density functional theory study,
Inorg. Chem. 48 (2009) 8415–8422, https://doi.org/10.1021/ic901014r.
[37] P.A. Mane, S. Dey, A.K. Pathak, M. Kumar, N. Bhuvanesh, Xantphos-capped Pd(II)
and Pt(II) macrocycles of aryldithiolates: structural variation and catalysis in C-C
coupling reaction, Inorg. Chem. 58 (2019) 2965–2978, https://doi.org/10.1021/
acs.inorgchem.8b02726.
´
[60] R.A. Singer, M. Dore, J.E. Sieser, M.A. Berliner, Development of nonproprietary
phosphine ligands for the Pd-catalyzed amination reaction, Tetrahedron Lett. 47
(2006) 3727–3731, https://doi.org/10.1016/j.tetlet.2006.03.132.
[61] C.A. Fleckenstein, H. Plenio, 9-Fluorenylphosphines for the Pd-catalyzed
Sonogashira, Suzuki, and Buchwald-Hartwig coupling reactions in organic solvents
and water, Chem. - A Eur. J. 13 (2007) 2701–2716, https://doi.org/10.1002/
chem.200601142.
[38] A.E.W. Ledger, A. Moreno, C.E. Ellul, M.F. Mahon, P.S. Pregosin, M.K. Whittlesey,
J.M.J. Williams, Pincer phosphine complexes of ruthenium: formation of Ru(P-O-
P)(PPh 3)HCl (P-O-P = xantphos, DPEphos, (Ph2PCH 2CH2)2O) and Ru(dppf)
(PPh3)HCl and characterization of cationic dioxygen, dihydrogen, dinitrogen, and
arene coordinated phosphine products, Inorg. Chem. 49 (2010) 7244–7256,
https://doi.org/10.1021/ic100438d.
[62] N. Schwarz, A. Tillack, K. Alex, I.A. Sayyed, R. Jackstell, M. Beller, A novel
palladium catalyst for the amination of electron-rich indole derivatives,
Tetrahedron Lett. 48 (2007) 2897–2900, https://doi.org/10.1016/j.
tetlet.2007.02.082.
[63] S. Doherty, J.G. Knight, C.H. Smyth, G.A. Jorgenson, Electron-rich, bicyclic biaryl-
Like KITPHOS monophosphinesvia [4+2] cycloaddition between 1-alkynylphos-
[39] D.J. Fox, S.B. Duckett, C. Flaschenriem, W.W. Brennessel, J. Schneider, A. Gunay,
R. Eisenberg, A model iridium hydroformylation system with the large bite angle
ligand xantphos: reactivity with parahydrogen and implications for
hydroformylation catalysis, Inorg. Chem. 45 (2006) 7197–7209, https://doi.org/
10.1021/ic060731l.
–
phine oxides and anthracene: highly efficient ligands for palladium-catalysed C
N
–
and C C bond formation, Adv. Synth. Catal. 350 (2008) 1801–1806, https://doi.
org/10.1002/adsc.200800307.
[64] C.M. So, Z. Zhou, C.P. Lau, F.Y. Kwong, Palladium-catalyzed amination of aryl
mesylates, Angew. Chemie - Int. Ed. 47 (2008) 6402–6406, https://doi.org/
10.1002/anie.200802157.
[40] H. Nie, Y. Zhu, X. Hu, Z. Wei, L. Yao, G. Zhou, P. Wang, R. Jiang, S. Zhang,
Josiphos-type binaphane Ligands for iridium-catalyzed enantioselective
hydrogenation of 1-aryl-substituted dihydroisoquinolines, Org. Lett. 21 (2019)
8641–8645, https://doi.org/10.1021/acs.orglett.9b03251.
[65] K. Suzuki, Y. Hori, T. Kobayashi, A new hybrid phosphine ligand for palladium-
catalyzed amination of aryl halides, Adv. Synth. Catal. 350 (2008) 652–656,
https://doi.org/10.1002/adsc.200700543.
[41] Q. Shen, T. Ogata, J.F. Hartwig, Highly reactive, general and long-lived catalysts
for palladium-catalyzed amination of heteroaryl and aryl chlorides, bromides, and
iodides: scope and structure-activity relationships, J. Am. Chem. Soc. 130 (2008)
6586–6596, https://doi.org/10.1021/ja077074w.
[66] G.J. Withbroe, R.A. Singer, J.E. Sieser, Streamlined synthesis of the bippyphos
family of ligands and cross-coupling applications, Org. Process Res. Dev. 12 (2008)
480–489, https://doi.org/10.1021/op7002858.
[42] J. Meng, M. Gao, H. Lv, X. Zhang, Highly enantioselective hydrogenation of o-
alkoxy tetrasubstituted enamides catalyzed by a Rh/(R, S)-josiphos catalyst, Org.
Lett. 17 (2015) 1842–1845, https://doi.org/10.1021/acs.orglett.5b00401.
[43] A.T. Lindhardt, T.M. Gøgsig, T. Skrydstrup, Studies on the 1,2-migrations in Pd-
catalyzed negishi couplings with JosiPhos ligands, J. Org. Chem. 74 (2009)
135–143, https://doi.org/10.1021/jo801824e.
[67] M.M. Heravi, N. Nazari, Bischler-Napieralski reaction in total synthesis of
isoquinoline-based natural products. An old reaction, a new application, Curr. Org.
Chem. 19 (2015) 2358–2408, https://doi.org/10.2174/
1385272819666150730214506.
[68] R. Pratap, D. Parrish, P. Gunda, D. Venkataraman, M.K. Lakshman, Influence of
biaryl phosphine structure on C-N and C-C bond formation, J. Am. Chem. Soc. 131
(2009) 12240–12249, https://doi.org/10.1021/ja902679b.
[44] A.A. Ibrahim, P.H. Wei, G.D. Harzmann, N.J. Kerrigan, Josiphos-catalyzed
asymmetric homodimerization of ketoketenes, J. Org. Chem. 75 (2010)
7901–7904, https://doi.org/10.1021/jo101867m.
[69] J. Ruan, L. Shearer, J. Mo, J. Bacsa, A. Zanotti-Gerosa, F. Hancock, X. Wu, J. Xiao,
Paracyclophane-based monophosphine ligand for palladium-catalyzed cross-
coupling reactions of aryl chlorides, Org. Biomol. Chem. 7 (2009) 3236–3242,
https://doi.org/10.1039/b906139h.
[45] S.K. Gibbons, R.P. Hughes, D.S. Glueck, A.T. Royappa, A.L. Rheingold, R.B. Arthur,
A.D. Nicholas, H.H. Patterson, Synthesis, structure, and luminescence of copper(I)
halide complexes of chiral bis(phosphines), Inorg. Chem. 56 (2017) 12809–12820,
https://doi.org/10.1021/acs.inorgchem.7b01562.
[70] K. Suzuki, Y. Hori, T. Nishikawa, T. Kobayashi, A. Novel, (2,2-Diarylvinyl)
phosphine/Palladium catalyst for effective aromatic amination, Adv. Synth. Catal.
349 (2007) 2089–2091, https://doi.org/10.1002/adsc.200700220.
[71] B. Punji, J.T. Mague, M.S. Balakrishna, Synthesis of neutral (PdII, PtII), cationic (Pd
II), and water-induced anionic (PdII) complexes containing new mesocyclic
thioether-aminophosphonite ligands and their application in the Suzuki cross-
coupling reaction0, Inorg. Chem. 45 (2006) 9454–9464, https://doi.org/10.1021/
ic061419e.
[46] S.U. Son, K.H. Park, Y.S. Lee, B.Y. Kim, C.H. Choi, M.S. Lan, Y.H. Jang, D.J. Jang, Y.
K. Chung, Synthesis of Ru(II) complexes of N-heterocyclic carbenes and their
promising photoluminescence properties in water, Inorg. Chem. 43 (2004)
6896–6898, https://doi.org/10.1021/ic049514f.
[47] T.Y. Li, X. Liang, L. Zhou, C. Wu, S. Zhang, X. Liu, G.Z. Lu, L.S. Xue, Y.X. Zheng, J.
L. Zuo, N -heterocyclic carbenes: versatile second cyclometalated ligands for
neutral iridium(III) heteroleptic complexes, Inorg. Chem. 54 (2015) 161–173,
https://doi.org/10.1021/ic501949h.
[72] B. Punji, J.T. Mague, M.S. Balakrishna, Thioether-functionalized ferrocenyl-bis
(phosphonite), Fe{(C 5H4)P(-OC10H6(μ-S)C 10H6O-)}2: synthesis, coordination
´
ˇ ˇ
´
ˇ ˇ
[48] J. Vrana, J. Holub, Z. Ruiszickova, J. Fanfrlík, D. Hnyk, A. Ruiszicka, Investigation
of thiaborane closo-nido conversion pathways promoted by N-heterocyclic
carbenes, Inorg. Chem. 58 (2019) 2471–2482, https://doi.org/10.1021/acs.
inorgchem.8b03037.
behavior, and application in Suzuki-Miyaura cross-coupling reactions, Inorg.
Chem. 46 (2007) 10268–10275, https://doi.org/10.1021/ic701537k.
[73] B. Karimi, P. Fadavi Akhavan, A study on applications of N-substituted main-chain
NHC-palladium polymers as recyclable self-supported catalysts for the suzuki-
miyaura coupling of aryl chlorides in water, Inorg. Chem. 50 (2011) 6063–6072,
https://doi.org/10.1021/ic2000766.
[49] F. Fantuzzi, C.B. Coutinho, R.R. Oliveira, M.A.C. Nascimento, Diboryne
Nanostructures stabilized by multitopic n-heterocyclic carbenes: a computational
study, Inorg. Chem. 57 (2018) 3931–3940, https://doi.org/10.1021/acs.
inorgchem.8b00089.
[74] K.V. Vivekananda, S. Dey, D.K. Maity, N. Bhuvanesh, V.K. Jain, Supramolecular
macrocyclic Pd(II) and Pt(II) squares and rectangles with aryldithiolate ligands and
their excellent catalytic activity in suzuki C-C coupling reaction, Inorg. Chem. 54
(2015) 10153–10162, https://doi.org/10.1021/acs.inorgchem.5b00806.
[75] L.M. Zhang, H.Y. Li, H.X. Li, D.J. Young, Y. Wang, J.P. Lang, Palladium(II) chloride
complexes of N,N′-disubstituted Imidazole-2-thiones: syntheses, structures, and
catalytic performances in Suzuki-Miyaura and sonogashira coupling reactions,
[50] A. Kausamo, H.M. Tuononen, K.E. Krahulic, R. Roesler, N-heterocyclic carbenes
with inorganic backbones: electronic structures and ligand properties, Inorg.
Chem. 47 (2008) 1145–1154, https://doi.org/10.1021/ic7020929.
[51] T.I. Kückmann, U. Abram, Rhenium(V) oxo complexes with N-heterocyclic
carbenes, Inorg. Chem. 43 (2004) 7068–7074, https://doi.org/10.1021/
ic0497578.
16

Y. Absalan et al.
Journal of Photochemistry & Photobiology, A: Chemistry 417 (2021) 113346
Inorg. Chem. 56 (2017) 11230–11243, https://doi.org/10.1021/acs.
effects, Angew. Chemie - Int. Ed. 45 (2006) 4321–4326, https://doi.org/10.1002/
anie.200601253.
inorgchem.7b01616.
[76] A.V. Vorogushin, X. Huang, S.L. Buchwald, Use of tunable ligands allows for
intermolecular Pd-catalyzed C-O bond formation, J. Am. Chem. Soc. 127 (2005)
8146–8149, https://doi.org/10.1021/ja050471r.
[82] G.L, A. Najibi, The nonlocal kernel in van der waals density functionals as an
additive correction: an extensive analysis with special emphasis on the B97M-V
and ωB97M-V approaches, J. Chem. Theory Comput. 11 (2018) 5725–5738.
[77] S.A. Dandekar, S.N. Greenwood, T.D. Greenwood, S. Mabic, J.S. Merola, J.
M. Tanko, J.F. Wolfe, Synthesis of succinimido[3,4-b]indane and 1,2,3,4,5,6-hex-
ahydro-1,5- methano-3-benzazocine-2,4-dione by sequential alkylation and
intramolecular arylation of enolates derived from N,N,N’N’-
[83] F.W, R. Ahlrichs, No Title, Phys. Chem. 7 (2005) 3297.
[84] P. Comba, A. Merbach, The titanyl question revisited, Inorg. Chem. 26 (1987)
1315–1323, https://doi.org/10.1021/ic00255a024.
[85] B.C, Satyendra N. Shukla, Pratiksha Gaur, Dimple Dehariya, Schiff base complexes
of titanocene dichloride: synthesis, characterization, dft modeling, Antibacterial
and catalytic activity, Int. J. Basic Appl. Chem. Sci. 9 (2019) 1–20.
[86] M.S. Oderinde, N.H. Jones, A. Juneau, M. Frenette, B. Aquila, S. Tentarelli, D.
W. Robbins, J.W. Johannes, Highly chemoselective iridium photoredox and nickel
catalysis for the cross-coupling of primary aryl amines with aryl halides, Angew.
Chemie. 128 (2016) 13413–13417, https://doi.org/10.1002/ange.201604429.
[87] E.B. Corcoran, M.T. Pirnot, S. Lin, S.D. Dreher, D.A. Dirocco, I.W. Davies, S.
L. Buchwald, D.W.C. Macmillan, Aryl amination using ligand-free Ni(II) salts and
photoredox catalysis, Science (80-.) 353 (2016) 279–283, https://doi.org/
10.1126/science.aag0209.
tetramethylbutanediamides and N,N,N’N’-tetramethylpentanediamides, J. Org.
Chem. 64 (1999) 1543–1553, https://doi.org/10.1021/jo982000b.
[78] S. Tcyrulnikov, M.C. Kozlowski, Accounting for strong ligand sensitivity in Pd-
catalyzed α-arylation of enolates from ketones, esters, and nitroalkanes, J. Org.
Chem. 85 (2020) 3465–3472, https://doi.org/10.1021/acs.joc.9b03203.
[79] M.C. Willis, D. Taylor, A.T. Gillmore, Palladium-catalyzed intramolecular O-
arylation of enolates: application to benzo[6]furan synthesis, Org. Lett. 6 (2004)
4755–4757, https://doi.org/10.1021/ol047993g.
[80] Z.F. Xu, C.X. Cai, M. Jiang, J.T. Liu, Copper-catalyzed regio- and stereoselective O-
arylation of enolates, Org. Lett. 16 (2014) 3436–3439, https://doi.org/10.1021/
ol501434d.
[88] J.B. Diccianni, T. Diao, Mechanisms of nickel-catalyzed cross-coupling reactions,
Trends Analyt. Chem. 1 (2019) 830–844, https://doi.org/10.1016/j.
trechm.2019.08.004.
[81] C.H. Burgos, T.E. Barder, X. Huang, S.L. Buchwald, Significantly improved method
for the pd-catalyzed coupling of phenols with aryl halides: understanding ligand
17