View
62
Download
0
Category
Tags:
Preview:
Citation preview
Faculty of Chemistry and Chemical Engineering
“Babes-Bolyai” University
M. Kogălniceanu 1, 400082
Cluj-Napoca, Romania
Larisa-Natalia POPA (MĂTĂRÂNGĂ-POPA)
NOVEL PRECURSORS FOR CHARGE-TRANSPORT MATERIALS
BASED ON PHENOTHIAZINE DERIVATIVES
- ABSTRACT –
Scientific Advisors:
Prof. Dr. LuminiŃa SILAGHI-DUMITRESCU
Prof. Dr. Ioan A. SILBERG
- Cluj-Napoca 2009 -
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 2 - 2
Faculty of Chemistry and Chemical Engineering
“Babes-Bolyai” University
M. Kogălniceanu 1, 400082
Cluj-Napoca, Romania
Larisa-Natalia POPA (MĂTĂRÂNGĂ-POPA)
- Phd Abstract Thesis -
Jury
President
Prof. Dr. Ion Grosu, “Babeş-Bolyai” University, Cluj-Napoca, Romania
Reviewers
Prof. Dr. Ionel Mangalagiu, “Al. I. Cuza” University, Iasi, Romania
Assoc. Prof. Dr. Castelia Cristea, “Babeş-Bolyai” University, Cluj-Napoca, Romania
Assoc. Prof. Dr.Antal Csampai, „ ELTE” University, Budapesta, Hungary
Scientific Advisors
Prof. Dr. LuminiŃa Silaghi-Dumitrescu, “Babeş-Bolyai” University, Cluj-Napoca,
Romania
Prof. Dr. Ioan A. Silberg, “Babeş-Bolyai” University, Cluj-Napoca, Romania
Defence: 7th of October 2009
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 3 - 3
Table of contents
1. Introduction…………………………………………………………………………….. 6
2. General presentation of the phenothiazines ….…………………………………. 9
2.1 Generalities about the synthesis and the reactivity of phenothiazines….. 10
3. ORIGINAL CONTRIBUTIONS 17
3.1 Cyano(oligo)phenothiazines ………………………...…………………….. 18
3.1.1 Literature data on the aromatic nitriles……………………………. 18
3.1.2 Literature data on the oligophenothiazines………………………. 20
3.1.3 Synthesis and electronic properties of cyano (oligo)phenothiazines..... 24
3.2 Aminomethylene(oligo)phenothiazines……………………………………….. 39
3.2.1 Literature data on the mesoporous silicas……………………….. 39
3.2.2 Synthesis and electronic properties of aminomethylen
(oligo)phenothiazines………………………………………………..
39
3.3 Diphenothiazine dumbbells bridged by heterocycles……………………... 45
3.3.1 Literature data on the N, N- aryl substituted phenothiazines…... 45
3.3.2 Synthesis and electronic properties of diphenothiazine dumbbells
bridged by heterocycles………………………………..
48
3.4 Photoactive binaphthyl phenothiazine derivatives…………………………. 66
3.4.1 Literature data on the binaphthyl derivatives…………………….. 66
3.4.2 Synthesis of photoactive binaphthyl phenothiazine derivatives... 70
3.5 Phenothiazine Tröger Base derivatives………………………………………. 75
3.5.1 Literature data on the Tröger Base derivatives………………….. 75
3.5.2 The syntheses and electronic properties of phenothiazine Tröger
Base derivatives……………………………………………
76
4. Experimental part………………………………………………………...................... 84
4.1. General considerations………………………………………………………. 85
4.2. Syntheses of the precursors…………………………………………………. 86
4.2.1 Syntheses of N-Alkylphenothiazine……………………………….. 86
4.2.1.1 Synthesis of N-Methylphenothiazine (1)………………... 87
4.2.1.2 Synthesis of N-Hexylphenothiazine (2)…………………. 87
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 4 - 4
4.2.2 Synthesis of bromophenothiazine derivatives…………………… 88
4.2.2.1 Synthesis of3-Bromo-10-methyl-10H-phenothiazine(4). 88
4.2.2.2 Synthesis 3-Bromo-10-hexyl-10H-phenothiazine (5)..... 89
4.2.2.3 Synthesis of 3,7´´-Dibromo-10,10´,10´´-trihexyl
10H,10´H,10´´H- [3´,7;7´,3´´]terphenothiazine (10)......
90
4.2.3 Synthesis of 10-Hexyl-3-(4,4,5,5-tetrametyl-1,3,2-dioxaborolan-2-
yl)-10H-phenothiazine (39)...............................
91
4.2.4 Synthesis of 3-bromo-10,10´´-dihexyl-10H,10´ H-[3,3´]
bisphenothiazine (7)...................................................................
92
4.2.5 Synthesis of 2,5- Dibromofurane (24)…………………………….. 93
4.2.6 Synthesis of 3,6 - Dibromo-9,9-dihexyl-9H-fluorene (28)............ 93
4.2.7 Synthesis of (RS)-N,N’-diacetyl-1,1’-binaphthalene-2,2’
diamine (40)…………………………………………………………
94
4.2.8 Synthesis of (RS)-N,N’-Diacetyl-6,6’-dibromo-1,1’ binaphthalene-
2,2’-diamine (41)………………………………….
94
4.2.9 Synthesis of (RS)-6,6’-Dibromo-1,1’-binaphthalene-2,2’-
diamine (42)………………………………………………………….
95
4.2.10 Synthesis of (R,S) 6,6’-Dibromo-1,1’-binaphthalene-2,2’-
dicarbonitrile (43).......................................................................
95
4.2.11 Synthesis of (R)-1,1’-Binaphthyl-2,2’-dimethyl ether(42)……… 96
4.2.12 Synthesis of (R) 6,6′-Dibromo-2,2′-dimethoxy-1,1′-binaphthyl
(43)…………………………………………………………………….
96
4.3 Syntheses of the (oligo)phenothiazinyl nitriles 11 – 18……………………. 97
4.3.1 Synthesis of 3-Cyano-10-methyl-10H-phenothiazine (11)……… 103
4.3.2 Synthesis of 3-Cyano-10-hexyl-10H-phenothiazine (12)……….. 103
4.3.3 Synthesis of 3,7-Dicyano-10-hexyl-10H-phenothiazine (13)…… 104
4.3.4 Synthesis of 3-Cyano-10,10´-dihexyl-10H,10´H-3´,7-
bisphenothiazine (14)……………………………………………… 105
4.3.5 Synthesis of 3,7´-Dicyano-10,10´-dihexyl-10H,10´H-3´,7-
bisphenothiazine (15)………………………………………………
106
4.3.6 Synthesis of 3-Cyano-10,10´,10´´-trihexyl-10H,10´H,10´´H-[3´,7;
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 5 - 5
7´,3´´]terphenothiazine (17)………………………………... 106
4.3.7 Synthesis of 3,7´´-Dicyano-10,10´,10´´-trihexyl 10H,10´H,10´´H-
[3´,7; 7´,3´´]terphenothiazine (18)……………..
107
4.4 Synthesis of aminomethylen (oligo)phenothiazines 19 – 25……………… 108
4.4.1 Synthesis of 10-Methyl-10H-phenothiazine- 3-methylenamine
(19)…………………………………………………………………….
109
4.4.2 Synthesis of 10-Hexyl-10H-phenothiazine- 3-methylenamine
(20)…………………………………………………………………….
109
4.4.3 Synthesis of 10-Hexyl-10H-phenothiazine- 3,7
dimethylenamine (21)………………………………………………
110
4.4.4 Synthesis of 10,10´-Dihexyl-10H,10´H-3´,7-bisphenothiazine-3-
methylenamine (22)……………………………………………...
110
4.4.5 Synthesis of 10,10’-diheyl-10H, 10H’-3,3’-biphenothiazine-7,7’-
diyl dimethylenamine (23)…………………………………….
111
4.5 Synthesis of new phenothiaizine dyads 30, 31, 32, 33, 34, 35 and 37….. 112
4.5.1 Synthesis of10, 10’-Biphenothiazinyl-2,5-furane (30)…………… 114
4.5.2 Synthesis of 10, 10’-Biphenothiazinyl-3,6-pyridazine (31)……… 114
4.5.3 Synthesis of 10, 10’-Biphenothiazinyl-2,5-pyridine (32)………… 115
4.5.4 Synthesis of 10, 10’-Biphenothiazinyl-2,6-pyridine (33)………… 115
4.5.5 Synthesis of 3,6-[10,10’]Biphenothiazinil-9,9-dihexyl-9H- fluorene
(34)………………………………………………………...
116
4.5.6 Synthesis of 10, 10’-Biphenothiazinyl-2,5-thiophene (35)……… 117
4.5.7 Synthesis of 10-Acenaphtalen-5yl-10H-phenothiazine (37)……. 117
4.6 Synthesis of (R,S) 6,6’-Bis-(N-hexylphenothiazin-3-yl)-1,1’-binaphthalene -
2,2’-dicarbonitrile (44)………………………………………
118
4.7 Synthesis of (R,S) 2,2’ –Bis (N-hexylphenothiazin-3-yl) 1,1’-binaphthalene
(45)………………………………………………………….
119
4.8 Syntheses of 2-aminophenothiazines……………………………………… 119
4.8.1 Synthesis of 10H-phenothiazine- 2-amine (50)………………… 120
4.8.2 Synthesis of 10- Methyl-10H-phenothiazine- 2-amine (51)…… 120
4.9 Syntheses of phenothiazines Tröger’s Bases…………………………….. 121
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 6 - 6
4.9.1 Synthesis of 6H, 2H-tetrahydro-10’H, 10’’H-phenothiazinyl-[1,5]
diazocine (52)…………………………………………………
121
4.9.2 Synthesis of 6H, 2H-tetrahydro-10’Me, 10’’Me-phenothiazinyl
-[1,5]diazocine (53)…………………………………………………
122
5. General conclusions………………………………………………………………….. 123
6. References……………………………………………………………………………… 127
Appendix (A)………………………………………………………………........................... 139
A.1 Abbreviations…………………………………..…………………………….... 140
A.1.1. General abbreviations……………………………………………. 140
A1.2 Abbreviations for groups and substituents………………. 141
A1.3 Abbreviations for NMR, IR and mass spectra…………... 141
A.2 Crystal data and structural refinement……………………………………… 143
A2.1 Data for 2,5-Di(10H-phenothiazin-10-yl)thiophen 35.........…… 143
A2.2 Data for 3,6-[10,10’]Biphenothiazinil-9,9-dihexyl-9H-fluorene
34……………………………………………………………………
144
A.3 Coordinates of 10, 10’-Biphenothiazinyl-3,6-pyridazine 31 and
10,10’-Biphenothiazinyl-2,5-thiophene from molecular modelling 35…...
145
A 3.1 Cartezian coordinates (B3LYP/6-31+G(d,p)) of 31……………. 145
A 3.2 Cartezian coordinates (B3LYP/6-31+G(d,p)) of 35……………. 146
A.4 List of the synthesized compounds…………………………………………. 149
List of scientific communications………………………………………………………...
152
Keywords: Phenothiazine, nitrilephenothiazine, dumbbell-shaped diphenothiazines,
binapthyl-phenothiazine, Tröger’s base, palladium, fluorescence, cyclic votammetry.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 7 - 7
1. Introduction
The chemistry of phenothiazine derivatives is a long-standing and continuously
active field, inspired in part by their application in medicine and these derivatives have
become important spectroscopic probes in molecular and supramolecular arrangements.
The main purpose of this work is to obtain phenothiazine precursors for novel
charge-transport materials.
The original results for the synthesis and characterisation of new phenothiazine
derivatives with different subtituentes like nitriles, amines, heterocycles, their reactivity
and potential application in materials science are presented.
We have synthesized the 3-cyano and 3,7-dicyano (oligo)phenothiazines, which
were obtained in good to very good yields from bromo (oligo)phenothiazines via the
Beller cyanation protocol either under conductive or under dielectric heating using NMP
as a solvent. These cyano(oligo)phenothiazines display large Stokes-shifts (5800–8300
cm-1
) and substantial quantum yields (11–27%).
Dumbbell-shaped diphenothiazines with heterocyclic bridges display tunable
redox and in some cases, fluorescence properties. New phenothiazine dyads were
synthesized in good to very good yields using the Buchwald-Hartwig amination of
phenothiazine with different dibromo aromatic heterocycles: electron-deficient units such
as pyridine, pyridazine and electron-rich units like thiophene, furane, fluorene. The
symmetrical dumbbell-shaped phenothiazine dyads bridged by heterocycles show intense
electronic coupling between the redox-active phenothiazine moieties. The fluorescence of
the pyridyl-bridged derivatives can be controlled by pH change giving reversibly
switchable redox-active bielectrophore dyads.
The preparation of new phenothiazin - binaphthalene derivatives following a
rational synthetic approach based on Suzuki or Negishi arylation of suitable precursors, is
discussed. These compounds are candidates for new molecular materials with potentially
efficient photoinduced electron transfer properties due the low-oxidation potential and
high tendency to form stable radical cations of the phenothiazine units.
The first synthesis of innovative phenothiazine Tröger’s base derivatives was
prepared and their conformations are proposed and has been investigated using DFT
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 8 - 8
calculations. These derivatives present remarkable Stokes-shifts (6900-7400cm -1
) and
substantial quantum yields (29 - 40%).
3. ORIGINAL CONTRIBUTION
3.1 Synthesis and electronic properties of cyano(oligo)phenothiazines
Due to their rich transformation potential and with regard to grafting and fine-
tuning of electronic properties we have focussed on cyano(oligo)phenothiazines.
Cyanophenothiazines are usually prepared either by de novo synthesis of the phenothiazinyl
core or by elimination from amides or oximes1.
(Oligo)phenothiazinyl nitriles were synthesized in good to very good yields from
bromo (oligo)phenothiazines via the Beller cyanation protocol either under conductive or
under dielectric heating using NMP as a solvent (Scheme 1).
N
S Br
nhexyl
H
n
N
S CNH
n
K4[Fe(CN6)], Na2CO3
[Pd(OAc)2, dppf], NMP120 °C, 20 h
orMW (160 °C), 1 h
N
S Br
nhexyl
Br
n
N
S CN
nhexyl
NC
n
nhexyl
5: n = 1 7: n = 210: n = 3
K4[Fe(CN6)], Na2CO3
[Pd(OAc)2, dppf], NMP120 °C, 20 h
orMW (160 °C), 1 h
12: n = 1 14: n = 2 17: n = 3 11-82%
7: n = 1 8: n = 210: n = 3
13: n = 1 15: n = 2 18: n = 3 35-86%
Scheme 1. Synthesis of cyano(oligo)phenothiazines 11 - 18
The structures of the (oligo)phenothiazinyl nitriles 11-18 are unambiguously supported
by 1H and
13C NMR spectroscopy and mass spectrometry and correct combustion
analysis. All the nitrile derivatives show in carbon-nuclear magnetic resonance spectrum
1 a) Vowinkel, E.; Bartel, J. Chem. Ber. 1974, 107, 1221; b) Burger, A.; Schmalz, C. J.
Org. Chem. 1954, 19, 1841; c) Cauquil, G.; Casadevall, A. Bull. Soc. Chim. Fr.
1955, 1061; d) Abramov, I. G.; Zhandarev, V. V.; Smirnov, A. V.; Kalandadze, L. S.;
Goshin, M. E.; Plakhtinskii, V. V. Mendeleev Commun. 2002, 3, 120.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 9 - 9
the characteristic signal for the carbon atom from CN group in δ = 105-110 ppm region
(Figure 1). In the case of bisnitrilephenothiazine derivatives NMR spectra show the Cs
symmetry which becomes clear by half number of signals. In the IR spectra the absobtion
due to the vibration of CN group appears at 2220-2250 cm-1
, which reveal the typically
absorptions for phenothiazinnitrile derivatives.
Figure 1. The 1H NMR (500 MHz) and
13C NMR (125 MHz) of 12 in CD2Cl2
Their electronic properties (Table 3) were determined by absorption and emission
spectroscopy and cyclic voltammetry. All compounds display intense blue to greenish-
blue daylight fluorescence with fluorescence quantum yields between 11 and 27 % and
remarkable Stokes shifts (5800-8300 cm-1
). These substantial Stokes shifts can be
attributed to significant geometrical changes upon excitation from a highly non-planar
ground-state to a largely planarized excited state2. According to absorption and emission
spectra the effective conjugation length is already reached with two conjugatively linked
phenothiazinyl units. In particular, the emission data can be attributed to the presence of a
3-cyano phenothiazinyl moiety (17) which seems to be the dominant fluorophore.
2 L. Yang, J.-K. Feng, A-M Ren, J. Org. Chem. 2005, 70, 5987–5996.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 10 - 10
Table 1. Electronic properties of the cyano (oligo)phenothiazines 11-18.
Compound
Absorption
λmax,abs
[nm][a]
Emission
λmax,em
[nm][a]
Quantum
yield
[%][b]
Stokes
shift
(cm-1
)
E00/+1
[mV] [c]
E0+1/+2
[mV]
E0+2/+3
[mV]
11 267, 336 475, 505
(sh) - 8600 - - -
12 268, 340 474, 491
(sh.) 11 8300 952 - -
13 277, 335,
366
479, 507
(sh.) 19 6400 1179 - -
14 279, 324,
375
481, 507
(sh.) 25 5800 711 1040 -
15 281, 333,
376
481, 510
(sh.) 18 5900 936 1098 -
17 282, 328,
376
474, 491
(sh.) 27 5800 631 781 1012
18 281, 333,
377
474, 491
(sh.) 22 5800 656 981 1030
[a] Recorded in CH2Cl2 [b] Determined with coumarine 1 as standard. [c] Recorded in
CH2Cl2, 20 °C, v = 100 mV/s, electrolyte: nBu4N
+ PF6
-, Pt working electrode, Pt counter
electrode, Ag/AgCl reference electrode.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 11 - 11
3.2 Synthesis and electronic properties of aminomethylene(oligo)phenothiazines
Since the discovery of mesoporous silicas in 19923,4
,
research on these materials
has rapidly developed. They can be readily obtained by micellar condensation of silicic
acid derivatives.
Our goal was to synthesize new molecules which contain both 10H-phenothiazine
and triethoxysilyl units for adsorption on silica surfaces. In this way, functionalized silica
surfaces which exhibit phenothiazine properties (fluorescence, redox activity, etc.) can be
obtained. The cyanophenothiazines 11, 12, 13 and 14 were reduced to the corresponding
amines 19, 20, 21 and 22 with LiAlH4 in diethyl ether (Scheme 2). Unfortunately, we
didn’t succeed to reduce the dicyano dyads, monocyano and dicyano triads because of the
low solubility of these compounds in diethyl ether, THF and toluene. In order to reduce
the dicyanophenothiazynil dyad we have tried to used the tetra-n-
butylamoniumborohydrid5 as reducing agent in CH2Cl2 (Scheme 2). This procedure
afforded the corresponding amino derivatives in 83% yields.
N
S
R
N
S
R
CNXNH2Y
LiAlH4, Et2Oreflux
or
Bu4NBH4
CH2Cl2, ref lux
n n
11 : n =1, R = Me, X = H12 : n =1, R = Hex, X = H13 : n =1, R = Hex, X = CN14 : n =2, R = Hex, X = H15 : n =2, R = Hex, Y = CN
19 : n =1, R = Me, Y = H
20 : n =1, R = Hex, Y = H
21 : n =1, R = Hex, Y = CH2NH2
22 : n =2, R = Hex, Y = H
23 : n =2, R = Hex, Y = CH2NH2
40-92%
Scheme 2. Synthesis of amino(oligo)phenothiazines.
The structures of the (oligo)phenothiazinyl methylen amines 19-23 are
unambiguously supported by 1H and
13C NMR spectroscopy and mass spectrometry and
correct combustion analysis.
3 a) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J. S. Nature
(London, U.K.) 1992, 359, 710; b) Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M.
E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T. W.; Olson, D. H.; Sheppard, E. W.;
McCullen, S. B.; Higgins, J. B.; Schlenker, J. L. J. Am. Chem. Soc. 1992, 114, 10834. 4 a) Soler-Illia, G. J. de A. A.; Sanchez, C.; Lebeau, B.; Patarin, J. Chem. ReV. 2002, 102,
4093; b) Widenmeyer, M.; Anwander, R. Chem. Mater. 2002, 14, 1827. 5 T. Wakamatsu, H. Inaki, A. Ogawa, M. Watanabe, Y. Ban, Heterocycles 1980, 14 (10),
1437
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 12 - 12
The electronic properties of the (oligo)phenothiazine amines 19 - 23 were investigated
by absorption and emission spectroscopy and cyclic voltammetry (table 2). Furthermore,
the fluorescence quantum yield of 22 was determined with coumarine 1 as standard.
Table 2. Electronic properties of the amino (oligo)phenothiazines 19 - 23.
PT
Absorption
λmax,absnma
Emission
λmax,em [nm][a]
Quantum
yield[%][b]
E00/+1
[mV] [c]
E0+1/+2
[mV]
Stokes-
Shifts
(cm-1
)
19 260, 286 - - 701 - -
20 260, 314 - - 743 - -
21 260, 316 479, 507 (sh) - 739 - 11700
22 270, 325, 284 460, 485 (sh.) 13 634 853 9030
23 288, 237, 370d 470, 504 (sh)
d - 628 845 5700
[a] Recorded in CH2Cl2 [b] Determined with coumarine 1 as standard. [c] Recorded in
CH2Cl2, 20 °C, v = 100 mV/s, electrolyte: nBu4N
+ PF6
-, Pt working electrode, Pt counter
electrode, Ag/AgCl reference electrode [d] Recorded in DMSO
3.3 Synthesis and electronic properties of diphenothiazine dumbbells bridged by heterocycles
New phenothiazine dyads were synthesized in good to very good yields using the
Buchwald-Hartwig amination of phenothiazine with different dibromo aromatic
heterocycles. Electron-deficient units were used as spacer like pyridine, pyridazine and
electron-rich units like thiophene, furane, fluorene.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 13 - 13
Scheme3. Synthesis of new phenothiazines dyads.
The structures of the phenothiazine dyads 30-35 are unambiguously supported by
1H and
13C NMR spectroscopy, mass spectrometry and correct combustion analysis.
The electronic structures of some heterocycle-bridged phenothiazine dyads 31 and
35 was considered by computations on the DFT level of theory (B3LYP/6–
31+G(d,p))6.The structures of 3,6-pyridazine- 31 (Figure 2) and 2,5-thiophene- 35
(Figure 3) bridged phenothiazine dyads were geometry optimized and for further
discussion the electron density distribution in the frontier orbitals (HOMO and LUMO)
of these lowest energy conformation structures was exclusively taken into account.
donors whilst the thiophene moiety serves as an acceptor.
Figure 2. LUMO(left) and HOMO(rigth) of the N,N’-pyridazine bridged biphenothiazine
31
6 M. J. Frisch, et al., Gaussian 03, Revision C.03; Gaussian, Inc.,Wallingford, CT, USA,
2004.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 14 - 14
Figure 3. LUMO(left) and HOMO(right) of the N,N’-thiophene bridged biphenothiazine
35.
Most characteristically, the butterfly structure of the phenothiazinyl moieties is
reproduced by the computations. Futhermore, both phenothiazine units adopt the
pseudo-equatorial intra-configuration, which is typical for N-aryl phenothiazines7.
Due to symmetry, the computed HOMO (Figure 19, right) is predominately localized
on both phenothiazine moieties, whereas the LUMO (Figure 19, left) is localized on
the central thiophene. This also represents the intuitive notion, where phenothiazine
units can be regarded as strong electron donors whilst the thiophene moiety serves as
an acceptor. The electronic structure of 31 with respect to the frontier orbitals reveals
a significantly different electron distribution (Figure 20) in comparison with the
thiophene derivative 35. While the LUMO (Figure 20, left) of 31 is located mostly in
the pyrazidine moiety, the HOMO (Figure 20, right) represents a largely delocalized
structure, i.e. electron density in all fragments of the molecule.
The electronic properties of the phenothiazine dyads 30 – 35 were investigated by
absorption and emission spectroscopy and cyclic voltammetry (table 3). Optical
spectroscopy studies (UV/Vis and fluorescence spectra) of systems 30 – 35 displays
weak fluorescence with emission of blue-green light and enormous Stokes shifts (9600-
10600 cm-1
). Since pyridazine itself is essentially non-fluorescent8, expectedly, the
pyridazine bridged phenothiazine derivative 31 does not show any detectable emission.
7 J.-P. Malrieu and B. Pullman, Theor. Chim. Acta 1964, 2, 293. 8 H. Li, P. Dupre and W. Kong, Chem. Phys. Lett. 1997, 273, 272.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 15 - 15
Table 3. Electronic properties of the phenothiazines 30 – 36.
Compound Absorption
λmax,abs [nm][a]
Emission
λmax,em [nm][a]
Stokes
Shifts
[cm-1
]
E00/+1
[mV] [b]
E0+1/+2
[mV] [b]
30 252, 304 443, 503 (sh.) 10300 608 954
31 253, 303 - - 851 1155
32 253, 283, 309 517, 556 (sh.) 13000 736 1132
33 288, 251, 333 516, 552 (sh.) 10600 891 1276
34 259, 280, 308 477, 506 (sh.) 11500 761 -
35 256, 311 444, 512 (sh.) 9600 640 1072
36 260, 299, 313 473 10800 716 -
[a] Recorded in CH2Cl2 [b] Recorded in CH2Cl2, 20 °C, v = 100 mV/s, electrolyte: nBu4N
+ PF6
-, Pt working electrode, Pt counter electrode, Ag/AgCl reference electrode.
The fluorescence was monitored upon titration with trifluoroacetic acid (TFA)
in methylene chloride (Figure 4). The fluorescence of both compounds 32 and 33
develops in a similar fashion upon continuous addition of aliquots of TFA. Whereas
the free bases 32 and 33 display emission at 516 nm and 517nm, respectively, after
addition of 0.1-5 equivalents of TFA the emission is noticeably quenched.
Figure 4. Emission spectra of 32 (left) and 33(right) in the presence of increasing
amounts of TFA(recorded in CH2Cl2, c(9) = 10-6
M, T = 293k)
According to cyclic voltammetry symmetrical dumbbell-shaped phenothiazine
dyads bridged by heterocycles show intense electronic coupling between the redox-active
350 400 450 500 550 600 6500
50
100
150
200
250
300
350
Em
issio
n
wavelength [nm]
0 eq
0.1eq
0.2eq
0.3eq
0.5eq
1eq
2eq
3eq
5eq
350 400 450 500 550 600 6500
50
100
150
200
250
300
0 eq
0.1 eq
0.2 eq
0.3 eq
0.5 eq
1 eq
2 eq
3 eq
10 eq
5 eq
Em
issio
n
Wavelength [nm]
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 16 - 16
phenothiazine moieties. Futhermore, the fluorescence of the pyridyl-bridged derivatives
can be controlled by pH change giving reversibly switchable redox-active bielectrophore
dyads.
3.4 Photoactive binaphthyl phenothiazine derivatives
We aimed to prepare a series of binaphthyl derivatives bearing phenothiazine
groups at positions 2,2’ and/or 6,6’. Investigation of the photochemical and
electrochemical properties of such derivatives should give as valuable information about
electronic communication among these groups via binaphthyl spacer as a background for
construction of optoelectronic devices.
The preparation of new bis-(10-alkyl-phenothiazin-3yl)-1,1’-binaphthalene
derivatives following a rational synthetic approach based on Suzuki or Negishi arylation
of suitable precursors, is discussed. Positive results were obtained by Suzuki arylation of
the (RS)-6,6’-dibromo-[1,1’-binaphthalene]-2,2’-dicarbonitrile with 10-Hexyl-3-(4,4,5,5-
tetrametyl-1,3,2-dioxaborolan-2-yl)-phenothiazine and Negishi arylation of the (RS)-2,2’-
diiodo-[1,1’-binaphthalene] with 3-bromo-10-hexyl-phenothiazine.
CN
CN
Br
Br
S
N
nHex
B
O
O
(Ph3P)4Pd
DME
80o C
CN
CN
S
N
nHex
S
N
nHex
43 39 44
72 %
S
N
nHex
Br
5
S
N
nHex
S
N
nHex45
I
I
DIBN
Pd[(PPh3)4]
27%
Scheme 4. Synthesis of new binaphtalen phenothiazines 44 and 45
The structure of compound 44 is supported by 1H-NMR and
13C-NMR. The values of
chemical shifts and the coupling constants for the protons of the oligomer 44 are
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 17 - 17
presented in Table 4. Most characteristically for all N-hexyl-subtituted phenothiazines the
methylene protons apeear as a triplet at δ = 3.80 ppm with vicinal coupling constant of
7.3 Hz. For the aromatic phenothiazinyl binapthyl protons resonances, well resolved
coupling patterns of the signals are found between δ = 6.80 – 8.42 ppm. In particular, the
nitril binaphtyl phenothiazine 44 can be clearly identified by the diagnostic appearance
by quaternary carbon nuclei at δ = 99 ppm in the 13
C-NMR spectra. The characteristic
CN- triple bond of 44 stretching vibration at 2160 cm-1
in the IR spectra reveal the
typically absorptions for nitrile derivatives.
Table 4. The values of chemical shifts and coupling constants of the protons in the
structure of diciano binaphtalen phenothiazine 44.
Type of compound Type of proton
Chemical shift
δ (ppm)
Coupling
constant
J (Hz)
t 6H
m 12H
m 4H
t 4H
m 12H
m 6H
d 2H
dd 3H
dd 3H
0.87
1.29
1.67
3.80
6.80
7.60
7.84
8.17
8.42
7.3 (J)
7.3 (J)
8.5 (J)
2.0 (J) 8.5 (J)
2.0 (J) 8.5 (J)
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 18 - 18
3.5 Phenothiazine Tröger Base derivatives These work is dedicated to Prof.Univ. Dr. Ioan A. Silberg
Tröger’s base was first synthesized in 1887 by Julius Tröger9, and its V-shaped
and rigid structure has attracted a lot of attention in the past years10
that has led to
applications in the design of various receptors for the recognition of neutral organic
molecules such as menthol11
or adenine12
as well as for the recognition of dicarboxylic
acids13
, and it has been used as a chiral auxiliary for the enantioselective synthesis of
aziridines14
.
Our approach is aimed at the formation of self-assembled helical phenothiazine
Troger Base.
We found that the heating the mixture at 60°C for 4h and after that the mixture
was stirred at room temperature for 48h give us the better yields of the Troger’base
analogues 52 (23%) and 53 (40%) in oil bath (Scheme 5).
Scheme 5. Synthesis of the phenothiazine Troger Base derivatives 52 and 53
The structures of the aminophenothiazine and Troger’s Base derivatives are
unambiguously supported by IR, 1H NMR spectroscopy and mass spectrometry.
9 J. Tröger, J. Prakt. Chem. 1887, 36, 225.
10 M. Valik, R. M. Strongin, V. Kral, Supramol. Chem. 2005, 17, 347.
11 a) M. D. Cowart, I. Sucholeiki, R. R. Bukownik, C. S. Wilcox, J. Am. Chem. Soc.
1988, 110, 6204; b) T. H. Webb, H. Suh, C. S. Wilcox, J. Am. Chem. Soc. 1991, 113,
8554. 12
a) J. C. Adrian Jr, C. S. Wilcox, J. Am. Chem. Soc. 1989, 111, 8055; b) J. C. Adrian Jr,
C. S. Wilcox, J. Am. Chem. Soc. 1991, 113, 678; c) J. C. Adrian Jr, C. S. Wilcox, J. Am.
Chem. Soc. 1992, 114, 1398. 13
a) S. Goswami, K. Ghosh, Tetrahedron Lett. 1997, 38, 4503– 4506; b) S. Goswami, K.
Ghosh, S. Dasgupta, J. Org. Chem. 2000, 65, 1907. 14
Y.-M. Shen, M.-X. Zhao, J. Xu, Y. Shi, Angew. Chem. 2006, 118, 8173.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 19 - 19
The electronic properties of the phenothiazine derivatives 52 and 53 were investigated
by absorption and emission spectroscopy (Table 5). Furthermore, the fluorescence
quantum yields of these push-pull chromophores were determined with coumarine 1 as
standard.
Table 5. Electronic properties of the phenothiazines 50 - 53
Compounds
Absorption
λmax,abs
[nm][a]
Emission
λmax,em
[nm][a]
Quantum
yield
[%][b]
Stokes
shift
(cm-1
)
52
259, 339 442 40 6900
53
282, 342
460 29 7400
[a] Recorded in acetonitrile [b] Determined with coumarine 1 as standard.
Optical spectroscopy studies (UV/Vis and fluorescence spectra) of systems 52 -
53 display considerable fluorescence with emission of blue-green light with highest
fluorescence quantum yields between 29 and 40% and remarkable Stokes shifts (6900 –
7400 cm-1
). These substantial Stokes shifts can be assigned to significant geometrical
changes upon excitation from a highly non-planar ground-state to a largely planarized
excited state.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 20 - 20
5. General conclusions
The goal of this thesis was the synthesis and structural characterizaion of novel
phenothiazines derivatives with tunable electronic properties as precursors for charge-
transport materials.
During the work in this field, the obtaining of conjugated phenothiazine
containing heterocycless was analyzed and pursued.
The original contributions of this work, presented in chapters 3, are related to the
preparation and structural characterisation of nitril, amino phenotiazine oligomers,
dumbbell-shaped phenothiazine dyads, napthalen-phenothiazines and Tröger base
phenothiazines.
The results are summarized here:
seven nitrile phenothiazine oligomers were obtained and fully characterised.
We have transposed the Beller cyanation to electron rich phenothiazines,
predominantly under dielectric heating, giving rise to the formation of
(oligo)phenothiazinyl nitriles and dinitriles. The electronic properties, as determined
by absorption and emission spectroscopy and cyclic voltammetry, reveal a class of
highly fluorescent extended p-electron systems with large Stokes-shifts (5800-8300
cm -1
) and substantial quantum yields (11-27%). Furthermore, these
fluorophores are reversibly oxidized at potentials that correlate with the number of
phenothiazinyl units.
five aminomethylene phenothiazianes were obtained from the corresponding
cyano derivatives using two different reducing agents: LiAlH4 in EtO2 and
nBu4NBH4 in CH2Cl2 – solubility problems and they was fully characterised. Our
goal was to synthesize new molecules which contain both 10H-phenothiazine and
trietoxysilyl units for adsorption on silica surfaces. In this way, functionalized
silica surfaces which exhibit phenothiazine properties (fluorescence, low
oxidation potential etc.) can be obtained. The target molecules can be prepared
by reacting amines with phenothiazine units and 3-(triethoxysilyl)-propyl-
isocyanate.
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 21 - 21
seven dumbell-shaped phenothiazines were obtained and fully characterised. We
have presented the synthesis and electronic properties of dumbbell-shaped
phenothiazine dyads. The introduction of the heterocyclic bridge can be easily
accomplished by the Buchwald-Hartwig aryl amination. The symmetrical
systems 37, 40 and 42 show intense electronic coupling between the redox-
active phenothiazinyl units as shown by cyclovoltammetry. Futhermore, we
could demonstrate that the emission of derivatives 39 and 40 in CH2Cl2 can
be switched off by the addition of TFA and switched on by neutralizing the
sample solution as a consequence of the enhanced basicity of the pyridines by
the electron rich phenothiazine moieties.
two binaphthyl - phenothiazines were obtained and characterised by 1H and
13C
NMR. Despite the difficulties in coupling two electron-rich aromatic systems, the
results obtained using the palladium catalyzed cross-couplings reactions,
especially the Negishi coupling involving phenothiazinil-zincchloride derivatives
as intermediates, and the Suzuki coupling involving phenothiazinil borate
intermediates, opened us the way to achieve the synthesis of phenothiazine-
binaphthyl derivatives. The attempts to synthesize the full-conjugated tetra
substituted binaphthalene with phenothiazine have lead to complex mixtures. The
1HNMR experiments have revealed some characteristic signals of the desired
compounds, unfortunately, this compound could not been isolated in order to
perform a full characterization. The exploitation of cross-coupling methodologies
opens flexible strategies to various functionalization of naphthalen and
phenothiazinyl derivatives.
two phenothiazines Troger’s base were obtained and characterised by 1H NMR,
IR and MS spectroscopy. We have observed for the first time the formation of
phenothiazinyl Troger’s bases, which are the chiral amine with two stereogenic
nitrogen atoms and are bonded by a methylen bridge. The electronic properties, as
determined by absorption and emission spectroscopy, reveal a class of highly
fluorescent π-electron systems with remarkable Stokes-shifts (6900 - 7400cm-1
) and
substantial quantum yields (29 - 40%).
PhD Abstract Thesis – Larisa Natalia Popa (c. Mataranga-Popa)
- 22 - 22
The electronic properties of these derivatives were interesting related to the correlation
between structure and redox potential. Electronic coupling of the donor and the acceptor
in the excited state can be observed, which is in prospect an application of the substance
class for photoinduced electron transfer (PET) studies. Furthermore, for the bridged and
unbridged oligophenothiazines there is also a strong dependence of the electronic
communication between aromatic units on the distance of electrophores and the nature of
the bridge.
List of scientific communications
Published Pappers
1. Adam W. Franz, Larisa N. Popa, Frank Rominger and Thomas J. J. Müller, Org.
Biomol. Chem., 2009, 7, 469–475.
“First synthesis and electronic properties of diphenothiazine dumbbells bridged by
heterocycles”.
2. Adam W. Franz, Larisa N. Popa and Thomas J. J. Müller Tetrahedron Letters, 2008,
49(20), 3300-3303.
”First synthesis and electronic properties of cyano(oligo)phenothiazines”
3. Larisa N. Popa, M. Putala, Studia, 2007, LII, 4, 43-50.
“Photoactive binapthyl pehnothiazine derivatives”
Poster Presentations
1. “Dumbbell-shaped Phenothiazine Dyads Bridged by Heterocycles”
Larisa Natalia Popa, Adam Franz, Luiza Gaina, Luminita Silaghi-Dumitrescu, Thomas
J.J. Müller
2. „Utilisation des pheromones sexuelles des insectes pour la protection des arbres”
Popa Larisa, Pojar-Feneşan Maria, Oprean Ioan, Balea Ana, Pirlea Maria
Actes du troisieme Colloque Franco-Roumain de Chimie Applique COFrROCA , 22-26
septembrie 2004, Slanic-Moldova, Bacau – Romania.
Recommended