A. Kędzia, et al.
DyesandPigments172(2020)107865
155.4, 137.5 ppm; IR (ATR): ν = 3251, 3191, 3068, 2917, 1671, 1633,
procedure [45] from commercially available aroyl carboxylic acids. The
crude chlorides 9a-c (15 mmol) were dissolved in dry toluene (10 mL)
and added dropwise to the mixture of 1,2,4,5-tetrazine-3,6-dicarbohy-
drazide (6) (1.0 g, 5 mmol), sodium bicarbonate (1.26 g, 15 mmol) and
water (40 mL). Resulted slurry was mixed for 24 h at room temperature.
The plastic mass was cooled in an ice bath and filtered. The product was
treated with diethyl ether (40 mL), triturated and dried.
1601,1501, 1375, 1344, 1254, 1182, 1143, 1116 cm−1
;
UV/Vis
200 nm
(CH2Cl2):
λ
max(ε) = 274
(12743),
236
(14169),
(14347 mol−1dm3cm−1); fluorescence (CH2Cl2):
λ
ex = 289 nm;
λ
em = 377 nm; HRMS (ESI): m/z calcd for C6H2N8S2+H+: 250.9917
[M+H]+; found: 250.9919; elemental analysis calcd (%) for C6H2N8S2:
C 28.80, H 0.81, N 44.78; found: C 28.86, H 0.83, N 44.75.
4.2.4.2. 3,6-Di(5-methyl-1,3,4-thiadiazol-2-yl)-1,2,4,5-tetrazine
4.2.5.1. N′,N′-Bis(4-methoxybenzoyl)-1,2,4,5-tetrazine-3,6-
(8b). According to general procedure using conventional heating (72 h)
or microwave irradiation. The resulting mixture was filtrated and the
dicarbohydrazide (10a). According to general procedure. Pink solid
(2.04 g, 94% yield), mp. 185 °C, 1H NMR (400 MHz, [D6]DMSO):
δ = 10.85 (s, 2H; NH), 10.19 (s, 2H; NH), 7.90 (d, JH,H = 8 Hz, 4H;
Ar), 7.02 (d, JH,H = 8 Hz, 4H; Ar), 3.83 ppm (s, 6H; CH3); 13C NMR
(100 MHz, [D6]DMSO) δ = 167.0 (C]O), 162.8, 158.6, 157.5 (C]O),
131.3, 123.0, 113.8, 55.4 ppm (CH3); IR (ATR): ν = 2843, 2548, 1676,
1601, 1577,1516, 1427, 1325, 1298, 1258, 1179, 1165, 1179, 1165,
1130, 1106 cm−1; UV/Vis (MeOH): λmax(ε) = 253 (60867), 209 nm
filtrate was evaporated on
a rotary evaporator. Then, 30 mL of
chloroform was added to the residue and the precipitate was filtered
off and washed with another portion of pure chloroform (20 mL) giving
the yellow solid (0.50 g, 71% yield using conventional heating and
0.54 g, 77% yield using microwave irradiation), mp. 196 °C, 1H NMR
(400 MHz, [D6]DMSO): δ = 2.24 ppm (s, 6H; CH3); 13C NMR (100 MHz,
[D6]DMSO) δ = 167.8, 158.1, 155.6, 17.2 (CH3) ppm; IR (ATR):
ν = 3191, 3034, 1685, 1639, 1599, 1573, 1500, 1369, 1292, 1254,
1182, 1254, 1182, 1142, 1115 cm−1; UV/Vis (CH2Cl2): λmax(ε) = 279
(6512), 247 (7237), 229 (7930), 200 nm (10963 mol−1dm3cm−1);
fluorescence (CH2Cl2): λex = 291 nm; λem = 376 nm; HRMS (ESI): m/z
(43835 mol−1dm3cm−1); HRMS (ESI): m/z calcd for C20H18N8O6+H+
:
467.1422 [M+H]+; found: 467.1421; elemental analysis calcd (%) for
C20H18N8O6: C 51.50, H 3.89, N 24.03; found: C 51.43, H 3.88, N 24.06.
4.2.5.2. N′,N′-Bis[4-(dimethylamino)benzoyl]-1,2,4,5-tetrazine-3,6-
dicarbohydrazide (10b). According to general procedure. Yellow solid
(1.72 g, 70% yield), mp. 225 °C, 1H NMR (400 MHz, [D6]DMSO):
δ = 10.63 (s, 2H; NH), 10.53 (s, 2H; NH), 7.75 (d, JH,H = 8 Hz, 4H;
Ar), 6.70 (d, JH,H = 8 Hz, 4H; Ar), 2.99 ppm (s, 12H; CH3); 13C NMR
(100 MHz, [D6]DMSO) δ = 167.5 (C]O), 158.4, 157.8 (C]O), 153.0,
130.9, 117.1, 110.9, 39.7 ppm (CH3); IR (ATR): ν = 3191, 2913, 1663,
1600, 1496, 1370, 1318, 1293, 1232, 1185, 1123 cm−1; UV/Vis
calcd for C8H6N8S2+H+
: ; found: 279.0233;
279.0230 [M+H]+
elemental analysis calcd (%) for C8H6N8S2: C 34.53, H 2.17, N 40.26;
found: C 34.51, H 2.14, N 40.22.
4.2.4.3. 3,6-Di(5-ethyl-1,3,4-thiadiazol-2-yl)-1,2,4,5-tetrazine
(8c). According to general procedure using conventional heating (72 h)
or microwave irradiation. The resulting mixture was filtrated and the
filtrate was evaporated on
a
rotary evaporator. Then, 30 mL of
(MeOH):
λ
max(ε) = 308
(51219),
HRMS
228
(ESI):
(24405),
m/z calcd
206 nm
for
chloroform was added to the residue and the precipitate was filtered
and washed with another portion of pure chloroform (20 mL) giving the
white solid (0.43 g, 55% yield using conventional heating and 0.47 g,
61% yield using microwave irradiation), mp. 263 °C, 1H NMR
(400 MHz, [D6]DMSO): δ = 2.65 (q, JH,H = 6.7 Hz, 4H; CH2),
δ = 1.13 ppm (t, JH,H = 8 Hz, 6H; CH3); 13C NMR (100 MHz, [D6]
DMSO) δ = 167.5, 162.4, 155.8, 27.4 (CH2), 10.2 ppm (CH3); IR
(ATR): ν = 3297, 3189, 2994, 2907, 1699, 1660, 1610, 1488, 1390,
1347, 1295, 1258, 1198, 1115 cm−1; UV/Vis (CH2Cl2): λmax(ε) = 280
(6845), 242 nm (4606 mol−1dm3cm−1); fluorescence (CH2Cl2):
(30236 mol−1dm3cm−1);
C
22H24N10O4+H+: 493.2055 [M+H]+; found: 493.2052; elemental
analysis calcd (%) for C22H24N10O4: C 53.65, H 4.91, N 28.44; found: C
53.61, H 4.93, N 28.41.
4.2.5.3. N′,N′-Bis(4-nitrobenzoyl)-1,2,4,5-tetrazine-3,6-dicarbohydrazide
(10c). According to general procedure. Yellow solid (2.08 g, 84% yield),
mp. 259 °C, 1H NMR (400 MHz, [D6]DMSO): δ = 10.84 (s, 2H; NH),
10.19 (s, 2H; NH), 8.37–8.33 (m, 4H; Ar), 8.16–8.09 ppm (m, 4H; Ar);
13C NMR (100 MHz, [D6]DMSO) δ = 163.5 (C]O), 158.5, 157.2 (C]
O), 149.3, 138.3, 128.9, 123.7 ppm; IR (ATR): ν = 3448, 3301, 3199,
2965, 1696, 1679, 1659, 1634, 1605, 1511, 1289, 1337, 1299, 1257,
λ
ex = 293 nm;
C
λem = 363 nm; HRMS (ESI): m/z calcd for
10H10N8S2+H+: 307.0543 [M+H]+; found: 307.0540; elemental
analysis calcd (%) for C10H10N8S2: C 39.20, H 3.29, N 36.58; found:
C 39.23, H 3.24, N 36.60.
1139, 1109 cm−1
(26480), 206 nm (26356 mol−1dm3cm−1); HRMS (ESI): m/z calcd for
18H12N10O8+H+: 497.0912 [M+H]+; found: 497.0914; elemental
; UV/Vis (MeOH): λmax(ε) = 363 (32313), 260
C
4.2.4.4. 3,6-Di(5-phenyl-1,3,4-thiadiazol-2-yl)-1,2,4,5-tetrazine
(8d). According to general procedure using conventional heating (4 h)
or microwave irradiation. The resulting mixture was filtrated and the
analysis calcd (%) for C18H12N10O8: C 43.56, H 2.44, N 28.22; found: C
43.54, H 2.41, N 28.25.
filtrate was evaporated on
a
rotary evaporator. Then, 30 mL of
4.2.6. General procedure for the synthesis of hybrids 11a-c
chloroform was added to the residue and the precipitate was filtered
and washed with another portion of pure chloroform (20 mL) giving the
yellow solid (0.54 g, 53% yield using conventional heating and 0.59 g,
58% yield using microwave irradiation, mp. 279 °C, 1H NMR (400 MHz,
[D6]DMSO): δ = 8.16–8.09 (m, 4H; Ar), 7.83–7.79 (m, 2H; Ar)
7.61–7.58 ppm (m, 4H; Ar); 13C NMR (100 MHz, [D6]DMSO)
δ = 167.8, 165.1, 159.2, 132.2, 128.5, 127.4, 126.7 ppm; IR (ATR):
ν = 3187, 1605, 1545, 1501, 1461, 1370, 1294, 1255, 1180, 1142,
1114 cm−1; UV/Vis (CH2Cl2): λmax(ε) = 322 (9955), 260 (8075), 237
(8525), 201 nm (8940 mol−1dm3cm−1); fluorescence (CH2Cl2):
N,N′-Diacylhydrazines 10a-c (6.0 mmol) were suspended in dry
toluene (7 mL) and phosphorus oxychloride (3 mL, 32 mmol) or dicy-
clohexylcarbodiimide (3.8 g, 18 mmol) was added. The reaction was
carried out using conventional heating or microwave irradiation
(180 W) in five cycles of 90 s with 2 min intervals at the temperature
80–150 °C. The resulting mixture was filtrated and the filtrate was
evaporated on a rotary evaporator. The 50 mL of water was added to
the residue and the precipitate was filtered and washed with water
(20 mL).
λ
ex = 294 nm;
C
λ
em = 345 nm; HRMS (ESI): m/z calcd for
4.2.6.1. 3,6-Bis(5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl)-1,2,4,5-
tetrazine (11a). According to general procedure using phosphorus
oxychloride and microwave irradiation. Orange solid (0.13 g, 51%
yield).
18H10N8S2+H+: 403.0543 [M+H]+; found: 403.0545; elemental
analysis calcd (%) for C18H10N8S2: C 53.72, H 2.50, N 27.84; found:
C 53.74, H 2.54, N 27.86.
According to general procedure using dicyclohexylcarbodiimide and
microwave irradiation. The resulting mixture was filtrated and the fil-
trate was evaporated on a rotary evaporator. The residue was purified
4.2.5. General procedure for the synthesis of N,N′-diacylhydrazines 10a-c
Aroyl chlorides (9a-c) were prepared according to literature
6