Organosilver(I/II) catalyzed C-N coupling reactions-phenazines

Article abstract of DOI:10.1039/c3cy20798f

The paper reports organosilver catalyzed C-N coupling reactions of pyridyl (py) carbaldehydes and substituted anilines, thereby producing substantially different phenazines (PZs) with basic molecular skeletal and bulk N _py-substituents. The different chemical reactivity of N _py-substituted derivatives in polar protic solvents, in the presence of the Ag^I-salts, with the dinuclear silver(i/ii) organometallic precursors exhibiting C-Ag^I/II-Cl covalently bonded species, is described. The latter are elucidated fully by the theoretical quantum chemical method and experimentally evidenced by mass spectrometry in the gas phase (GP), involving a variety of ionization techniques. To our knowledge, we first report a comprehensive study of the nature of the organometallic precursors, which represents an important step of the catalyzed C-C and C-N coupling processes. Thus impacting all fields the enormous synthetic research efforts are focused on PZs, which through the diversity of the molecular architectures are main components observed in naturally occurring products (NPs), dyes, pesticides, antibiotics, etc. The emphasis of the paper is on the mass spectrometry (MS), employing its high-resolution power and accuracy of the analytical qualitative, quantitative and structural information as well as the physico-chemical thermodynamic one, at the analyte concentrations in the range of fg g ^-1. The latter, which are beyond the capability of other instrumental methods for structural analysis, make the MS an irreplaceable method in the advanced catalytical research. Its combined application with the method of the quantum chemistry provides reliable thermodynamic information in the condensed phase and in the GP, which helps understand comprehensively the mechanisms of the organometallic catalyzing processes, particularly the unique coupling reactions, thus improving significantly their effectiveness.

Full text of DOI:10.1039/c3cy20798f

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Organosilver(I/II) catalyzed C–N coupling
reactions – phenazines†
Cite this: DOI: 10.1039/c3cy20798f
Bojidarka Ivanova* and Michael Spiteller
The paper reports organosilver catalyzed C–N coupling reactions of pyridyl (py) carbaldehydes and
substituted anilines, thereby producing substantially different phenazines (PZs) with basic molecular
skeletal and bulk Npy-substituents. The different chemical reactivity of Npy-substituted derivatives in
polar protic solvents, in the presence of the AgI-salts, with the dinuclear silver(I/II) organometallic
precursors exhibiting C–AgI/II–Cl covalently bonded species, is described. The latter are elucidated fully
by the theoretical quantum chemical method and experimentally evidenced by mass spectrometry in
the gas phase (GP), involving a variety of ionization techniques. To our knowledge, we first report a
comprehensive study of the nature of the organometallic precursors, which represents an important
step of the catalyzed C–C and C–N coupling processes. Thus impacting all fields the enormous synthetic
research efforts are focused on PZs, which through the diversity of the molecular architectures are main
components observed in naturally occurring products (NPs), dyes, pesticides, antibiotics, etc. The
emphasis of the paper is on the mass spectrometry (MS), employing its high-resolution power and
accuracy of the analytical qualitative, quantitative and structural information as well as the physico-
chemical thermodynamic one, at the analyte concentrations in the range of fg gꢀ1. The latter, which
are beyond the capability of other instrumental methods for structural analysis, make the MS an
irreplaceable method in the advanced catalytical research. Its combined application with the method of
the quantum chemistry provides reliable thermodynamic information in the condensed phase and in
the GP, which helps understand comprehensively the mechanisms of the organometallic catalyzing
processes, particularly the unique coupling reactions, thus improving significantly their effectiveness.
Received 18th November 2012,
Accepted 5th January 2013
DOI: 10.1039/c3cy20798f
www.rsc.org/catalysis
interest in the development of synthetic approaches for obtaining
the substituted PZs consisted mainly in the CuII/I and PtII/IV
1. Introduction
catalyzed C–N coupling reactions.3 Recently very efficient synthetic
strategies have been developed; however, they use hindered sub-
strates, will occasionally be conducted at room temperature, longer
reaction times and relatively high loadings, low tolerance for
functional groups, low solubility in water, etc. Thus, the elabora-
tion of new approaches, involving catalysts, effective towards a
large number of functional groups and complexes of the highly
functionalized starting reagents, would be of great interest and
importance to push back the frontier of the advanced organic
synthesis. Our interest in PZs and oxazines, as main structural
motifs in naturally occurring humic substances,4 is based on
systematic efforts for elaboration of effective analytical methods
for environmental control of plant protecting agents against
susceptible bacterial and fungal pathogens.5 The PZs-producing
strains reside on roots, which can protect cultivated plants; there-
fore, the search for novel synthetic approaches of a large scale of
substituted PZs is of emergency. Here, we report an effectively
synthetic organosilver approach for functionalization of the PZs
The phenazines (PZs) are important molecular components
that can be found in a diverse number of NPs, dyes, pesticides,
antibiotics and others.1 Great interest in the functionalized PZs
is due to their excellent photo-physical and photochemical
properties with wide application in solar cell energy conversion
systems as well as their remarkable ability to coordinate
transition metal complexes with anticancer drugs due to their
strong stereo and sequence-specific interactions with the DNA
double helix. The light-switching effect and cytotoxic properties
of metal complexes of PZs from particularly ruthenium and
rhenium ones are determined.2 In this respect, the research
¨
¨
Lehrstuhl fur Analytische Chemie, Institut fur Umweltforschung,
¨
¨
¨
Fakultat fur Chemie, Universitat Dortmund, Otto-Hahn-Strasse 6, 44227 Dortmund,
North Rhine-Westphalia, Germany. E-mail: B.Ivanova@infu.uni-dortmund.de,
B.Ivanovaweb.de; Fax: +49 231 755 4084; Tel: +49 231 755 40 89
† Electronic supplementary information (ESI) available: Synthetic routes for 6–17
(Scheme S1); theoretical NBO analysis and qX(NBO) charges (X = C, N and O)
(Scheme S2); ESI–MS/MS spectra (Fig. S1). See DOI: 10.1039/c3cy20798f
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from substituted anilines and pyridyl-carbaldehydes in polar protic amounts of 50 mL and 5–15 mL ammonium hydroxide solution
solvents such as methanol or water. Its advantages consist in wide (NH4OH, ACS reagent, 28–30% NH3 base, Sigma Aldrich). To
functionalization tolerance, C–N cross-coupling reaction effective- thus-prepared solutions, 25 mL of each of the reagents (or their
ness under mild experimental conditions, easily accessible catalyst mixtures, Scheme 1; S1, ESI†) are added, i.e. N,N-diethyl-p-
and high catalytic activity. The comprehensive studies on organo- phenylenediamine (purity 97%), N,N-dimethyl-p-ethylenediamine
metallics catalyzing cross-coupling C–C for obtaining of the sym- (97%), 2-pyridinecarboxaldehyde (99%), 3-pyridinecarboxalde-
metrical and unsymmetrical biaryls, involved C–Mn+–Cl covalent hyde (98%), 4-pyridinecarboxaldehyde (99%) or 2-quinoline-
organometallic precursors (Mn+ = PtII/IV, PdII/III/IV, CuII/I, Hg0/I, AgI/III
,
carboxaldehyde (97%) (Sigma-Aldrich products as well) at
AuI/III and more which are important intermediates for the for- concentrations of 1 ꢁ 10ꢀ2 mol Lꢀ1, and recalculated to the
mation of the substituted phenyls and/or benzo[n]chromenes (n = 4 corresponding solvents or mixtures under stirring. Silver
or 6).6 The useful information regarding the catalytic activity of the nitrate (AgNO3, ACS reagents, AgI-salts, Sigma-Aldrich) in the
organosilver(I/II) precursors consists in the fact that the effort to amount ranging from 5.6–114 ng Lꢀ1 is added drop-wise to the
isolate oxazines from the starting substituted anilines and benz- reaction mixtures. 1-Cyclohexyl-pyridine-4-carbaldehyde iodide,
aldehydes resulted in selective formation of only the reported PZs 1-cyclohexyl-3-formyl-pyridinium iodide, 1-cyclohexyl-2-formyl-
in yields 56–78% and N-substituted 3,6,12,15-tetrahydro-9,18-dioxa- pyridinium iodide or 1-cyclohexyl-2-formyl-quinolinium iodide
3,6,12,15-tetraaza-phenanthro[9,10-b]triphenylenes. Since most of (R1 = C6H12, Scheme 1) used as reagents for the synthesis of 1–9
the reported 2-pyridyl derivatives are prepared through coupling
reactions such as Suzuki, Still, Grignard and Negishi, in the
presence of the above-mentioned transition metal catalyst, we
focused our attention on the corresponding 3- and 4-pyridyl
derivatives. Being heterocyclics, pyridyl-functional groups often
found in NPs possessed prominent broad spectrum of biological
activities, and are applied in pharmaceutical, agrochemical and
medicinal chemistry research.6,7 Despite the large number of
catalytic studies involving the silver-containing organometallics in
homogeneous catalysis, the structure and chemical mechanistic
states of the silver ions, electronic structures of the intermediates
and their physical properties remain elusive.3,7 To our knowledge,
this study for the first time in the literature, focused the attention
on the mechanistic aspects of the catalytic reactions, employing the
MS and the method of quantum chemistry, evidencing the for-
mation of dinuclear covalently bonded intermediates, in which the
metal centers formed C–AgI/II–Cl chromophores. In this respect,
mass spectrometry, with its capability to utilize different ionization
techniques, flexible sample preparation ones, and providing highly
precise analytical qualitative, quantitative and structural informa-
tion, even in the concentration range of fg (mL)ꢀ1, is a unique
irreplaceable method for physically elucidating the organometallic
precursors and catalysing processes.4,8 Furthermore, its combined
application with the method of the quantum chemistry helps study
the kinetics and the thermodynamics both theoretically and experi-
mentally and provides a unique opportunity to understand com-
prehensively the organometallic catalysing processes, and thus to
improve their effectiveness. In this context it is important to note
that the proposed involvement of the silver ions in the various
states in the oxidative homogeneous catalysis reported herein is
based on numerous heterogeneous catalysed coupling processes
where the silver is found in other forms of the oxidized states,
including initially the metallic silver and its oxide Ag2O.
2. Experimental
Synthesis
The synthesis is performed by the following method, involving
polar protic solvents such as water, methanol, and solvent
mixtures (CH3OH : H2O = 1 : 1 or H2O : CH3CN = 1 : 1) of Scheme 1 Chemical diagram of the phenazines and the organometallic precursors.
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are obtained by mixing equimolar amounts of iodocyclohexane 2,8-bis-dimethylamino-10H-phenazin-5-ol (13): found, C, 67.5;
(98%, copper as stabilizer) and above-mentioned aldehydes at r.t. H, 7.0; calcd [C16H20N4O], C, 67.6; H, 7.1%; 2,8-bis-diethyl-
under continuous stirring (yields 97–99%). The Npy-carbaldehydes, amino-10H-phenazin-5-ol (14): found, C, 70.6; H, 8.2; calcd
substituted by phenylamine, N,N-diethyl- or N,N-dimethyl aniline [C20H28N4O], C, 70.6; H, 8.3%; PZ (17): found, C, 76.1; H, 4.8;
residues (R1 = –C6H4–NH2, –C6H4–N(CH3)2 or –C6H4–N(CH2CH3)2, calcd [C48H36N8O2], C, 76.2; H, 4.8%; PZ (18): found, C, 78.2; H,
15–22) are obtained according to the proposed mechanisms. 6.9; calcd [C64H68N8O2], C, 78.3; H, 6.9%; PZ (19): found, C,
Determination of isolated substances is confirmed as well by 76.2; H, 4.7; calcd [C48H36N8O2], C, 76.2; H, 4.8%; PZ (20):
1H- and 13C-NMR methods and microanalysis.
found, C, 78.3; H, 6.8; calcd [C64H68N8O2], C, 78.3; H, 6.9%; the
The PZs 3,6,12,15-tetracyclohexyl-3,6,12,15-tetrahydro-9,18- 1H-NMR spectra of 11–14 showed –N(CH3)2 or –N(CH2CH3)2
dioxa-3,6,12,15-tetraaza-phenanthro[9,10-b]triphenylene (4) and proton signals d A 3.11–3.44 ppm as a six-proton sharp
(5) (retention time, RT = 9.21 and 9.24 min) revealed MS peaks singlet or quartet and triplet (2H and 3H). All aromatic
of K+-adducts of [M ꢀ H + K+]+ ions at 762 (Fig. S1, ESI†). 3,6,11- protons appeared in separate regions. The two aromatic protons
Tricyclohexyl-9-(1-cyclohexyl-1H-pyridin-4-ylidene)-6,9-dihydro- appeared as singlets at 7.60 and 6.88 ppm. The protons appearing
3H-3,6,11-triaza-benzo[b]triphenylen-14-one (2): found, C, 81.6; in the most down-field region at d 7.80 (1H, d, J = 7.6 Hz) are due
H, 8.0; calcd [C48H56N4O2], C, 81.7; H, 8.1%; 1H-NMR (400 MHz, to the proton m- to the –N(CH3)2 (resp. –N(CH2CH3)2) group.
CD3CN), d [ppm]: 3.21–3.56 (11H, m); 9.63 (2H, dd), 9.29 The other two protons in the same ring appeared at 7.41 (1H, dd,
(3H, dt), 8.44, 8.31 (4H, dd), 7.91 (2H, dd) and 7.80 (2H, dd); J = 2.4 Hz) and 6.73 (1H, d, J = 2.5 Hz), respectively.
13C-NMR: 92.1, 96.8, 102.3, 106.8, 110.4, 111.4, 112.4, 115.6,
Physical methods
121.4, 121.8, 122.5, 123.4, 123.7, 128.5, 129.3, 130.3, 130.4,
130.5, 131.2, 131.4, 131.5, 131.7, 131.9, 168.9, and 55.6–58.9, HPLC–ESI–MS/MS measurements are performed on a TSQ 7000
respectively. PZ (8): found, C, 72.1; H, 3.0; calcd [C24H12N4O2], instrument (Thermo Fisher Inc., Rockville, MD, USA), using the
C, 72.2; H, 3.1%; compound 8 and, similarly, 5, 21, and 22 mobile phases 0.1% v/v aqueous HCOOH, 0.1% v/v HCOOH in
exhibited in the 1H-NMR spectra 10 proton signals at 5.62–7.32 ppm CH3CN or in CH3CN : CH3OH = 1 : 1. For the electrospray
of the main conjugated [3,8]phenanthrolinium residue. The ionization mass spectrometric measurements is used a triple
carbon 13C-NMR signals are observed at 91.0–132.6 ppm, quadrupole mass spectrometer (TSQ 7000 Thermo Electron,
respectively. The R1 = –C6H11 substituents exhibited the series Dreieich, Germany) equipped with an ESI 2 source at the
of multiplets proton signals in the range of 2.22–3.21 ppm, following conditions: capillary temperature 180 1C; sheath gas
while at R1 = –C6H4–N(CH3)2 or –C6H4–N(CH2CH3)2 the aro- 60 psi, corona 4.5 mA and spray voltage 4.5 kV. Samples are
matic dd is observed in the range of 6.18–7.12 ppm. The proton dissolved in CH3CN (1 mg mLꢀ1) and are injected into the ion
signals of C6H4–N(CH3)2 are observed as singlet peaks at source by an auto-sampler (Surveyor) with a flow of pure CH3CN
3.45 ppm (s, 6H), while the –C6H4–N(CH2CH3)2 functional (0.2 mL minꢀ1). Data processing is performed by Excalibur 1.4
group showed peaks at 3.21 (4H, t) and 1.75 ppm (6H, t), software. A standard LTQ Orbitrap XL (Thermo Fisher Inc.)
respectively. 9,18-Dioxa-4,5,13,14-tetraaza-phenanthro[9,10-b]- instrument is used for UV–MALDI–Orbitrap–MS measure-
triphenylene (9): found, C, 72.2; H, 3.2; calcd [C24H12N4O2], C, ments, using the UV laser source at 337 nm. An overall mass
72.2; H, 3.1%; compound 9 and, in analogy, 4, 19, 20, 21 and 22 range of m/z 100–1000 is scanned simultaneously in the Orbi-
exhibited weakly perturbed proton chemical shift signals, trap analyzer. The ImageQuest 1.0.1 program package is used.
within the typical regions for those of the phenanthroline ones. The laser energy values are within 12.0–21.0 mJ. The number of
The 13C-NMR spectra revealed carbon signals of 9,18-dioxa- averaged laser shots lies within 8–109, the MALDI flow
3,6,12,15-tetraaza-phenanthro[9,10-b]triphenylene d A 90.0– rate values are within 21.2–23.4; the acquisition time is within
128.6 ppm, in addition to the peaks at 157.8, 160.3, 161.3, 22.7–133.2 min, the corresponding elapsed scan time range lies
and 161.7 ppm of the [1,4]dioxin residues. The 1H-NMR data of within 18.5–2.13 s, respectively. Chromatographic purification
R1-substituents showed Dd A 0.4–2.3 ppm to the above-stated is performed on a Gynkotek (Germering, Germany) HPLC
values. The tautomeric equilibrium i/ia (i = 3–5) is difficult to be instrument, equipped with a preparative Kromasil 100 C18
assigned by 1H- and 13C-NMR spectroscopy. The 2D analysis led column (250 ꢁ 20 mm, 7 mm; Eka Chemicals, Bohus, Sweden)
us to believe that the compounds existed exclusively in ia form, and a UV detector set at 250 nm. The mobile phase is
and the up-field shifting of the aromatic proton and carbon CH3CN : H2O (90 : 10, v/v) at a flow rate of 4 mL minꢀ1. The
signals of Dd A 0.5–0.7 and 0.3–1.4 ppm may be attributed to analytical HPLC is performed on a Phenomenex (Torrance, CA,
cumulative effects of adjacent substituents at R1-positions, USA) RP-18 column (Jupiter 300, 150 ꢁ 2 mm, 3 mm) under the
increasing the electron density at the pyridinium fragments same chromatographic conditions. The analysis is performed
by steric interactions. Dibenzo[b,j][4,7]phenanthroline-6,7-dione on a Shimadzu UFLC XR (Kyoto, Japan) instrument, equipped
(10): found, C, 77.3; H, 3.2; calcd [C20H10N2O2], C, 77.4; H, with an auto-sampler, PDA, an on-line degasser and column
1
3.3%; H-NMR: d, ppm 9.13 (s, 2H), 9.44 (s, 8H); N,N,N0,N0- thermostat. As stationary phase, a Phenomenex Luna Phenyl–
tetramethyl-5,10-dihydro-phenazine-2,8-diamine (11): found, Hexyl column (150 ꢁ 3 mm i.d., 3 mm particle size) is used. The
C, 71.0; H, 7.5; calcd [C16H20N4], C, 71.6; H, 7.5%; mobile phase consisted of 0.02% (v/v) TFA in water (solvent A)
N,N,N0,N0-tetraethyl-5,10-dihydro-phenazine-2,8-diamine (12): and acetonitrilemethanol 75 : 25 (v/v; solvent B). Separation is
found, C, 73.7; H, 8.6; calcd [C20H28N4], C, 74.0; H, 8.7%; achieved by a gradient analysis starting with 55A–45B, increasing
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the amount of solvent B in 30 min to 75% and 30.1 min to 100% molecules coordinated to the solute at the optimized geometry
B, stop time 40 min. For equilibration a post time of 15 min is of the super molecule. The protonation ability of the studied
applied. Other parameters: flow rate 0.30 mL minꢀ1, injection model systems was elucidated by the natural bond orbital
volume 5 mL, detection wavelength 280 nm; column tempera- (NBO) charges and analysis.10
ture T = 308 K. The UV–VIS and fluorescence spectra between
200 and 800 nm, using solvents (Uvasol, Merck product) at a
3. Results and discussion
concentration of 2.5 ꢁ 10ꢀ5 M, are recorded on a Tecan Safire
Absorbance/Fluorescence XFluor 4 V 4.40 spectrophotometer. The mechanistic aspect of the formation of PZs 1, 1a, 2, and
1
The H- and 13C- NMR measurements are performed at 298 K 15–18 (Scheme 1; S1, ESI†) is already comprehensively dis-
with a Bruker 400 DRX spectrometer using 5 mm tubes and cussed in metal-catalysing C–C coupling reactions, proposing
solvents D2O, CD3OD and CD3CN, mixtures D2O : CD3OD = a mononuclear organometallics intermediating species.6,7,11
1 : 1, D2O : CD3CN = 1 : 1, respectively. The chemical shift Furthermore, our MS data of Ib, showing the peaks at m/z
reference is sodium 3-(trimethylsilyl)tetradeuteriopropionate. 334/336 of [C12H18NOCl107Ag]+/[C12H18NOCl109Ag]+ ions, sup-
The EP data are obtained in the X-band on a Bruker ER 420 ported this assumption. The Ib revealed a high thermodynamic
spectrometer. The calorimetric (DSC) ones are performed on stability (DG = ꢀ397.17 kcal molꢀ1) which we explain, however,
DSC-2C Perkin Elmer equipment in argon. IR-spectra are with the charge localization on an AgII ion, obtained by a
recorded between 4000 and 400 cmꢀ1 on a Thermo Nicolet AgI - AgII redox-process, thus, revealing an electron configu-
6700 FTIR-spectrometer at 150 scans and resolution ꢂ1 cmꢀ1
.
ration of d9.76 of the metal centre. In this respect the synthesis
of PZs of dppz-type6,7,12 by C–N coupling reactions is as
expected. Nonetheless, we replace the usually involved Pd0/II
Computational methods
Chemometrics. The experimental and theoretical spectro- catalysts with salts of AgI ions. The reaction scheme for
scopic patterns are processed by R4Cal OpenOffice STATISTICs obtaining dppz involved the intermediate 7 from 6. In our
for Windows 79 program package. Baseline corrections and reaction protocol the yields of these derivatives are 47–52%.
curve-fitting procedures are applied. The chemometrics The novelty, however, consisted in isolation of the products 12,
involved the statistical significance of each regression coeffi- 12a and 14 of about 38–44%, which are explained with the
cient, checked by the t-test. The model fit is determined by the formation of the organometallics intermediates of type II. The
F-test.9
latter allowed us to obtain PZs 3–14, respectively. The experi-
Quantum chemical calculations. Quantum chemical calculations mental MS data revealed peaks at m/z 478/480/482, whose
were performed with Gaussian 09, Dalton 2011 and LSDALTON, elemental composition [C12H17Cl2NO107Ag]+/[C12H17Cl2NO109Ag]+
program packages.10 The geometries of the studied organic and isotopic shape assumed the formation of organometallic
species were optimized using second-order Moller–Plesset per- compound covalently bonded to C–AgI/II–Cl metal chromo-
turbation theory (MP2) and density functional theory (DFT). phores. The calculated thermodynamic parameters and NBO
The DFT method employed involved B3LYP, CAM–B3LYP, data of IIa and IIb species (Table 1) showed that DGIIa > DGIIb
and M06–2X functionals for organic compounds. The organo- (DDG = |62.78| kcal molꢀ1). Both metal ions revealed electronic
metallics ones were studied using the B3PW91 and M06–2X configurations of 4d4.88 and 4d4.87. Comparison with the thermo-
IIb
Ib
functionals. Molecular geometries were fully optimized by the dynamics of Ib, however, showed that ET o ET (DET
=
force gradient method using Berny’s algorithm. For every |607.33| kcal molꢀ1) while DGIIb > DGIb (DDG = |293.36| kcal molꢀ1),
structure the stationary points found on the molecule potential respectively. Therefore the obtained difference of the thermo-
energy hypersurfaces were characterized using standard dynamic stability of mono- and binuclear organometallics is
analytical harmonic vibrational analysis. The absence of the explained in electrostatic terms, since DETE = |287.01| kcal molꢀ1
.
,
imaginary frequencies, as well as of negative eigenvalues of the The tabulated data exhibited a significant contribution of ESP
Ib
second-derivative matrix, confirmed that the stationary points since ESP { ESPIIb, thus illustrating the impact of the solute–
correspond to minima of the potential energy hypersurfaces. solvent interactions, or in MS terms, the solute–continuum
The calculation of vibrational frequencies and infrared inten- interactions determined the stability of the organometallics in
sities was checked to establish which kind of calculations the ‘‘GP’’, respectively. Although, the obtained high thermo-
performed agree best with the experimental data. The dynamic stability of Ib may correlate to the higher yields of 2,
electronic spectra in gas phase and solution were obtained by in contrast to the corresponding products of type 4 and 5
time-dependent density functional (TD-DFT) method. The basis (yields 1–7%), respectively. The mechanism of producing
sets 6-311+G(2d,p), aug-cc-pVDZ and aug-cc-pVTZ were used for 11–14 involved the C–N formation with the participation of
organic molecules, while the SDD one was used for the corre- NH4OH, which has been already discussed in ref. 13. It is
sponding organometallics. To describe the species in aqueous important to note that the polar protic solvents, the catalytic
solution we use both an explicit super-molecule or micro- amounts of AgI-metal ions and basic (NH4OH) media are
hydration approach, in which several water molecules are important factors to obtain the above-mentioned products of
coordinated to the solute at the optimized geometry of the interactions through the organometallic intermediates of
super-molecule, and a polarizable continuum approach (PCM). type IIb, because only in the non-polar solvents the interaction,
The micro-hydration approach involved several water including those of the reported anilines and pyridine carbaldehydes
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Table 1 Theoretical NBO and thermodynamics of organometallics of types I–IIIa
Atom NEC
ET
EUPSS
EPSS
ESP
13.6
Ia AgI
Cl
5s0.304d4.915p0.016p0.01 ꢀ1204.2 ꢀ94.8 ꢀ121.5
3s0.993p2.89
Ib AgII
Cl
5s0.464d9.765p0.016p0.01 ꢀ1203.9 ꢀ157.4 ꢀ235.4 ꢀ169.0
3s1.983p5.73
IIa AgI
Cl
5s0.334d4.915p0.016p0.01 ꢀ1810.9 ꢀ43.5 ꢀ69.4
14.3
3s0.993p2.88
AgII
5s0.304d4.915p0.01
Cl
3s0.983p2.88
IIb AgII
Cl
5s0.334d4.875p0.016p0.01 ꢀ1811.3 ꢀ85.6 ꢀ163.6
46.3
Fig. 2 ESI–MS/MS spectra of 2.
3s0.993p2.85
AgI
5s0.274d4.885p0.016p0.01
3s0.983p2.84
Cl
IIIa AgI
Cl
5s0.334d4.736p0.01
3s0.973p2.69
ꢀ894.4 ꢀ65.0 ꢀ92.3
ꢀ894.4 ꢀ63.8 ꢀ89.3
17.4
16.5
9.8
IIIb AgII
Cl
5s0.354d4.716p0.01
3s0.973p2.65
IIIc AgI
Cl
5s0.794d9.805p0.026p0.02 ꢀ973.2 ꢀ35.3 ꢀ53.4
3s1.943p5.76
IIId AgII
Cl
5s0.074d4.766p0.01
ꢀ973.0 ꢀ63.9 ꢀ77.1
6.5
3s0.983p2.89
IIIe AgI
Cl
5s0.794d9.805p0.026p0.02 ꢀ1051.7 ꢀ33.7 ꢀ50.5
9.2
3s1.943p5.76
IIIf AgII
Cl
5s0.294d4.935p0.016p0.01 ꢀ1051.5 ꢀ58.8 ꢀ73.8
3s0.983p2.88
6.1
EET
GC
GD
GR
ETNE
DG
Ia ꢀ107.9 32.8
ꢀ34.4
9.2
7.0
5.7
8.5
4.1
3.6
4.2
4.2
4.9
4.3
7.6 ꢀ100.4
Ib ꢀ404.2 33.2
ꢀ33.0
ꢀ32.4
ꢀ34.9
ꢀ19.7
ꢀ19.2
ꢀ22.9
ꢀ22.9
ꢀ27.1
ꢀ26.2
7.3 ꢀ397.1
IIa
ꢀ55.1 39.8
13.1 ꢀ42.0
12.6 ꢀ104.8
4.9 ꢀ69.9
5.0 ꢀ67.8
5.9 ꢀ37.8
5.9 ꢀ64.8
5.4 ꢀ35.9
6.1 ꢀ61.6
IIb ꢀ117.4 39.1
IIIa ꢀ74.8 20.6
IIIb ꢀ72.8 20.6
IIIc ꢀ43.6 24.6
IIId ꢀ70.7 24.6
IIIe ꢀ41.2 27.6
IIIf ꢀ67.7 28.0
Fig. 3 ESI–MS spectra of 12, 12a, 12b and 14, respectively; chemical diagrams.
the M06–2X level of theory. A difference of Dlmax of about
1.4 nm is obtained.
a
ET – total free energy in solution with nonelectrostatic terms [a.u.];
Experimentally the band at 549 nm in 12 is explained by the
intramolecular charge transfer. It is interesting to mention the
role of the O-atom at the 12-position in the electronic transitions
in the oxazine dyes,4,6l shifted by about 35 nm. The heteronuclear
Diels–Alder reaction caused the formation of dimeric products
12a–14a (Fig. 3). The results are in agreement with the obtained
theoretical qX(NBO) values (X = N and O) exhibiting qN5/12(NBO) =
ꢀ0.410 and ꢀ0. 464, while qC4/6/11/13(NBO) are 0.111–0.147,
respectively. Furthermore the mechanistic aspects of such reac-
tions are already reported in a series of papers dedicated to the
synthesis and characterization of novel OLEDs based on the dppz-
dyes.6,7 The reaction scheme for formation of 15–22 involved the
N–pyridinium substituents (Scheme S1, ESI†) of phenylamine,
N,N-diethyl- or N,N-dimethyl aniline residues (R1 = –C6H5, –C6H4–
N(CH3)2 or –C6H4–N(CH2CH3)2), and making efforts to achieve the
corresponding oxazines involved the formation of the organo-
metallic precursors of type III (Scheme S2 and Fig. S1, ESI†). The
qC1(NBO) and qC4(NBO) values of 0.112, 0.123 and 0.127 make
favourable the formation of Ci–AgII–Cl covalently bonded species
(i = 1 or 4) in the polar protic solvents in the presence of AgI-ions,
since, however, we observed the MS peaks at m/z 234/236,
262/264 and 290/292 of the [C6H7107AgClN]+/[C6H7109AgClN]+,
[C8H11107AgClN]+/[C8H11109AgClN]+ and [C10H15107AgClN]+/
[C10H15109AgClN]+ organometallics (Fig. 4).
EUPSS – unpolar solute–solvent interaction energy [kcal molꢀ1]; EUPSS
–
polar solute–solvent interaction energy [kcal molꢀ1]; ESP – solute
polarization energy [kcal molꢀ1]; EET – total electrostatic energy [kcal molꢀ1];
GC – cavitation energy [kcal molꢀ1]; GD – dispersion energy [kcal molꢀ1];
GR – repulsion energy [kcal molꢀ1]; ENTE – total nonelectrostatic energy
[kcal molꢀ1]; DG – free Gibbs energy [kcal molꢀ1]; NEC – Natural
Electron Configuration.
resulted in the formation of organic dyes through the classical
Schiff’s synthetic routes.14 The electronic transitions of 12
and 14 (Fig. 1–3) in acetonitrile:methanol solvent mixtures
are correlated to corresponding theoretical values obtained at
Their further interactions with the Npy-benzaldehydes yielded
the dyes 15–22. In this context, the GP observation of III, in the
Fig. 1 Chromatogram and electronic transitions (UV-traces) of the obtained
phenazines.
c
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Acknowledgements
The authors thank the Deutscher Akademischer Austausch
Dienst (DAAD), and the Deutsche Forschungsgemeinschaft
(DFG); the central instrumental laboratories at the Dortmund
University (Germany) and the analytical and computational
laboratory clusters at the Institute of Environmental Research
(INFU) at the same university.
Fig. 4 ESI–MS spectrum of organometallic of type III.
positive MS operation mode assumed a AgI - AgII redox-
process.15 Nonetheless favourable for the inorganic com-
pounds of silver(I) is the AgI - AgIII process in alkaline media,
the stabilization of AgII-state is explained only by the formation
of C–Ag–Cl covalently bonded species. Furthermore, the com-
parison of theoretical thermodynamic and NBO data (Table 1)
showed that the AgI-organometallics are characterized by
higher DG values (IIIa, IIIc, IIIe), in contrast to the AgII-precursors
(IIIb, IIId, IIIf). These results assumed that the localization of
the charge on the metal ion led to an increase in the stability of
the species due to the electrostatic contributions, while its
localization on the N+(R3)2 moiety led to lower free energies
(DDG A |2.11|–|27.03| kcal molꢀ1). Interestingly, the absolute
charge values on metal centres in IIIa–f affected insignificantly
the NECs. The metal-to-ligand charge transfer effect is a domi-
nating one, thus causing electronic configuration of the metal
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The phenazines having substantially different basic molecular
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