FULL PAPER
A ketone-sensitized triplet population has been applied in
6H, Ar-H), 7.23±7.19 (m, 2H, Ar-H), 7.17±7.14 (m, 2H, Ar-H), 7.ꢀꢀ (2d,
J = 7.6 Hz, 2H, Ar-H), 6.93±6.91 (2d, J = 7.5 Hz, 2H, Ar-H), 4.ꢀ3±
3
3
[12±2ꢀ]
other cases.
The energy level of the triplet state (E ) of
T
1
3
3
.83 (2AA’BB’ spin systems, 4H, cyclobutane-H); C NMR (126 MHz,
): d = 162.4, 162.3 (CHO, CHO’), 139.5, 139.4, 138.9, 138.8, 138.1,
38.ꢀ, 137.1, 137.ꢀ (C4a, C4a’, C5a, C5a’, C9a, C9a’, C11a, C11a’), 131.5,
131.3, 131.1, 13ꢀ.9, 129.1, 128.9, 128.8, 128.7, 128.6, 128.5, 128.4, 128.4,
28.2, 127.9, 127.5, 127.3 (Ar-C), 49.4, 49.3, 48.5, 48.3 (C1ꢀ, C1ꢀ’, C11,
DBA should be comparable to that of cis-stilbene, 26ꢀ kJ
CDCl
1
3
ꢀ
1 [21]
mol . Direct and sensitized photoprocesses were recently
[17]
compared for bis-benzimidazole dyes and sulfur- or car-
[18]
1
boxy-substituted N-alkylphthalimides.
Electron transfer
+
+
C11’); MS (ESI, positive): m/z (%): 443 (1ꢀꢀ) [M] , 391 (2) [Mꢀ52] ,
occurs from the sulfur atom in methionine or cysteine deriv-
atives to the triplet state of 4-carboxybenzophenone in alka-
+
2
4
21 (3) [Mꢀ222] ; elemental analysis calcd (%) for C3ꢀ
22 2 2 w
H N O (M =
42.52): C 81.43, H 5.ꢀ1, N 6.33; found C 81.14, H 4.99, N 6.35.
[13±16]
line aqueous solution.
A further example for energy vs.
1
Photodimer of 16: M.p. 3ꢀ48C (lit. [8] 3ꢀꢀ±3ꢀ48C); H NMR (5ꢀꢀ MHz,
electron transfer is the combination of ketones and DNA
3
3
3
CDCl ): d = 7.69 (2d, J = 7.7 Hz, 4H, Ar-H), 7.59 (2d, J = 7.7 Hz, 2
[19,2ꢀ]
bases.
H, Ar-H), 7.43 (m, 2H, Ar-H), 7.34 (m, 6H, Ar-H), 7.18±7.ꢀ1 (m, 1ꢀH,
Ar-H), 6.85 (2d, 2H, Ar-H), 4.75±4.14 (m, 2AA ’BB’ spin systems, 4H,
Here, the photoprocesses of a series of DBA (1±14, 16±
2, Table 1) were studied by steady-state and time-resolved
1
3
cyclobutane-H); C NMR (126 MHz, CDCl
NCO’), 142.6, 141.9, 141.4, 137.7, 137.6, 137.2, 137.1, 135.1, 134.1, 133.9
C4a, C4a’, C5a, C5a’, C9a, C9a’, C11a, C11a’, NCO-C, NCO-C’), 132.1,
3
): d = 169.9, 168.3 (NCO,
2
spectroscopy as well as by preparative irradiations. The role
of the sensitizer and the effects of the molecular structure of
the DBA were investigated. It will be shown that efficient
triplet sensitization takes place in all cases while only N-acyl
and N-cyano derivatives are capable of photodimerization.
Reasons for the differing triplet reactivity will be discussed.
Furthermore, we prove that direct excitation clearly leads to
photodimers in considerable yield in a variety of N-acyl
DBA, clarifying the equivocal literature situation with
regard to non-sensitized photodimerizations.
(
131.6, 131.1, 13ꢀ.8, 13ꢀ.5, 13ꢀ.4, 13ꢀ.3, 13ꢀ.2, 13ꢀ.1, 129.5, 129.3, 129.1,
128.9, 128.8, 128.7, 128.6, 128.5, 128.4, 128.3, 128.2, 128.1, 128.ꢀ, 127.9,
1
27.8, 127.7, 127.3 (Ar-C), 48.8, 48.7, 46.4, 46.4 (C1ꢀ, C1ꢀ’, C11, C11’);
+
+
MS (ESI, positive): m/z (%): 653 (6) [M+58] , 595 (1ꢀꢀ) [M] ; elemen-
tal analysis calcd (%) for C42 (M = 594.71): C 84.82, H 5.ꢀ8, N
.71; found C 84.51, H 5.12, N 4.75.
Photodimer of 17: M.p.>3658C; MS (ESI, positive): m/z (%): 753 (13)
H
3ꢀ
N
2
O
2
w
4
+
+
[M+58] , 695 (1ꢀꢀ) [M] ; elemental analysis (%) calcd for: C H N O
2
5
ꢀ
34
2
(
M
w
= 694.83): C 86.43, H 4.93, N 4.ꢀ3; found C 86.6ꢀ, H 4.9ꢀ, N 4.ꢀ7.
Photodimer of 18: M.p. 3ꢀ5±3118C; MS (ESI, positive): m/z (%): 717
+
+
+
(
(
2ꢀ) [M+22] , 695 (1ꢀꢀ) [M] , 579 (12) [Mꢀ116] ; elemental analysis
%) calcd for: C5ꢀ
H
34
N
2
O
2
(M
w
= 694.83): C 86.43, H 4.93, N 4.ꢀ3; found
C 86.ꢀ5, H 4.96, N 4.ꢀ4.
1
Photodimer of 19: M.p. 327±3298C; H NMR (5ꢀꢀ MHz, CDCl
3
): d =
Experimental Section
7
.48±7.41 (m, 4H, Ar-H), 7.39±7.29 (m, 4H, Ar-H), 7.28±7.16 (m, 4H,
3
3
Ar-H), 7.ꢀ2( 2d , J = 7.9 Hz, Ar-H), 6.92( 2d , 2H,
.22±3.91 (m, 2AA’BB’ spin systems, 4H, cyclobutane-H); C NMR
126 MHz, CDCl ): d = 157.3 (2d, NCO, NCO’), 139.4, 139.2, 138.4,
38.2, 137.ꢀ, 136.9, 136.8, 136.6 (C4a, C4a’, C5a, C5a’, C9a, C9a’, C11a,
J = 7.8 Hz, Ar-H),
1
13
General: All H and C NMR spectra were recorded on a Bruker DRX
13
4
(
1
1
13
5
ꢀꢀ ( H: 5ꢀꢀ MHz; C: 126 MHz) spectrometer. NMR shifts refer to the
3
1
solvent signal as an internal standard (CDCl
3
, d = 7.25 for H and d =
1
3
7
7.ꢀ for C NMR). UV: polytec x-dap spectrometer. Fluorescence: Shi-
C11a’), 132.1, 131.8, 131.5, 131.3, 129.8, 129.1, 128.9, 128.8, 128.7, 128.6,
27.7, 127.5, 127.4, 127.3 (Ar-C), 116.7 (q, J(C,F) = 289 Hz, CO-CF
CO-CF ’), 48.4, 48.ꢀ, 46.8, 46.4 (C1ꢀ, C1ꢀ’, C11, C11’); elemental analysis
calcd (%) for C32
found C 66.23, H 3.49, N 4.86.
madzu RF-5ꢀꢀꢀ spectrometer. GC/MS: Hewlett Packard, model589ꢀ
with a HP5972detector. Elemental analyses were performed by the Insti-
tute of Organic Chemistry of the Technical University of Dresden (Ger-
many). Melting points are uncorrected.
1
3
,
3
H
2ꢀ
N
2
O
2
F
6
(M
w
= 578.51): C 66.44, H 3.48, N 4.84;
Solvents and chemicals: The solvents (Merck) were of the purest spectro-
scopic quality available, for example, acetone and acetonitrile: Uvasol;
methylcyclohexane (MCH) and 2-methyltetrahydrofuran (MTHF) were
purified by distillation. The sensitizers were used as received (acetophe-
none, Fluka) or purified by recrystallization (benzophenone and benzil).
Compound 1 was purchased from Acros Chimica and recrystallized three
times from ethanol.
1
Photodimer of 20: M.p. 331±34ꢀ8C (decomp.); H NMR (5ꢀꢀ MHz,
CDCl
7
3
): d = 7.54±7.49 (m, 4H, Ar-H), 7.36±7.3ꢀ (m, 4H, Ar-H), 7.25±
.17 (m, 4H, Ar-H), 6.99 (t, J = 7 Hz, 4H, Ar-H), 4.39±4.ꢀ5 (2AA’BB’
3
13
spin systems, 4H, cyclobutane-H); C NMR (126 MHz, CDCl
49.4, 149.3 (NCO, NCO’), 14ꢀ.8, 14ꢀ.6, 139.9, 139.8 (C4a, C4a’, C5a,
C5a’), 137.5, 137.4, 137.4, 137.3 (C9a, C9a’, C11a, C11a’), 131.6, 131.5,
31.4, 131.3, 129.4, 129.3, 129.2, 129.1, 128.9, 128.8, 128.6, 128.5, 127.6,
127.5, (Ar-C), 48.6, 47.5, 47.5 (C1ꢀ, C1ꢀ’, C11, C11’); MS (ESI, negative):
3
): d =
1
1
Preparation and characterization of dibenzazepine (DBA) derivatives:
The preparation and characterization of dibenzazepine derivatives are
described in the Supporting Information.
+
+
+
m/z (%): 511 (1ꢀꢀ) [M] , 465 (63) [Mꢀ46] , 415 (14) [Mꢀ96] , 311 (17)
+
+
[Mꢀ2ꢀꢀ] , 227 (23) [Mꢀ284]
; elemental analysis calcd (%) for
Characterization of photodimers: The photochemical formation and spec-
tral characterization of the photodimers of 10 and 14 has been described
3ꢀ 2ꢀ 2 2 2 w
C H N O Cl (M = 511.41): C 7ꢀ.46, H 3.94, N 5.48; found C 7ꢀ.69, H
3.97, N 5.51.
[
5]
[8]
1
elsewhere. In these and all other photodimers, the anti-configuration
Photodimer of 21: M.p. >36ꢀ8C (lit. 367±37ꢀ8C); H NMR (5ꢀꢀ MHz,
TFA + [D ]DMSO ext.): d = 7.54±7.48 (m, 4H, Ar-H), 7.35±7.34 (2d,
J = 7.5 Hz, 2H, Ar-H), 7.26±7.24 (m, 4H, Ar-H), 7.17±7.15 (2d, J =
7.5 Hz, 2H, Ar-H), 7.1ꢀ (d, J = 7.1 Hz, 1H, Ar-H), 7.ꢀ4 (d, J = 7.3 Hz,
1H, Ar-H), 6.99 (d, J = 7.5 Hz, 1H, Ar-H), 6.93 (d, J = 7.1 Hz, 1H,
Ar-H), 4.16±4.12(m, 2A A ’BB’ spin systems, 4H, cyclobutane-H);
NMR (126 MHz, TFA + [D ]DMSO ext.): d = 16ꢀ.1 (NCO, NCO’),
138.1, 137.9, 137.1, 136.9, 136.7, 136.4, 131.8, 131.6, 13ꢀ.8, 13ꢀ.6, 129.7,
128.9, 128.7, 128.1, 128.1, 127.1, 126.9, 125.8, 125.7 (Ar-C), 48.2, 48.1,
47.9, 47.7(C1ꢀ, C1ꢀ’, C11, C11’); MS (ESI, positive): m/z (%): 473 (1ꢀꢀ)
was concluded from the coupling pattern of the cyclobutane protons in
6
1
3
3
the H NMR spectra. For 9, 16, 19±21 two AA’BB’ spin systems were
1
3
3
found in the H NMR spectra of the cyclobutane protons. In these cases,
3
3
two rotamers of the dimers exist which originate from hindered rotations
1
3
of the amide CꢀN bonds, see ref. [5]
C
1
Photodimer of 8: M.p. 329±3328C; H NMR (5ꢀꢀ MHz, CDCl
3
): d =
6
3
3
7
.69 (d, 4H, Ar-H), 7.33 (t, J = 7.6 Hz, 4H, Ar-H), 7.17 (t, J = 7.5 Hz,
3
4
H, Ar-H), 7.ꢀ1 (d, J = 7.4 Hz, 4H, Ar-H), 4.25 (s, 4H, cyclobutane-H);
1
3
C NMR (126 MHz, CDCl
3
): d = 14ꢀ.4 (C4a, C4a’, C5a, C5a’), 136.ꢀ
+
+
+
(
C9a, C9a’, C11a, C11a’), 131.2, 128.9, 128.2, 123.2 (Ar-C), 114.6 (N-CN,
[M] , 391 (5) [Mꢀ82] , 236 (11) [Mꢀ237] ; elemental analysis calcd
+
+
N-CN’); MS (ESI, positive): m/z (%): 437 (77) [M] , 391 (1ꢀꢀ) [Mꢀ46] ,
(%) for C3ꢀ
H
24
N
4
O
2
(M
w
= 472.55): C 76.25, H 5.12, N 11.86; found C
+
+
+
1
93 (48) [Mꢀ244] , 171 (27) [Mꢀ266] , 149 (31) [Mꢀ288] ; elemental
76.ꢀ2, H 5.14, N 11.92.
analysis calcd (%) for C3ꢀ
H
2ꢀ
N
4
(M
w
= 436.52): C 82.55, H 4.62, N 12.84;
1
Photodimer of 22: M.p. 311±3138C; H NMR (5ꢀꢀ MHz, CDCl
.86 (d, J = 8.7 Hz, 4H, Ar-H), 7.77 (d, J = 7.1 Hz, 4H, Ar-H), 7.6ꢀ
3
): d =
found C 82.28, H 4.64, N 12.88.
3
3
7
1
3
3
Photodimer of 9: M.p. 339±34ꢀ8C; H NMR (5ꢀꢀ MHz, CDCl
3
): d =
(brs, 4H, Ar-H), 7.58 (t, J = 7.4 Hz, 2H, Ar-H), 7.46 (t, J = 7.5 Hz, 4
3
3
3
8
.85 (s, 2H, CHO), 7.44±7.41 (2d, J = 7.6 Hz, 2H, Ar-H), 7.38±7.3ꢀ (m,
H, Ar-H), 7.38 (d, J = 8.7 Hz, 4H, Ar-H), 7.35 (t, J = 7.4 Hz, 4H, Ar-
284
¹ 2ꢀꢀ4 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim