Compound characterization data — Kouame et al., 2026

Eric K. Kouame, Igor D. Poltavtsev, Anna A. Faizdrakhmanova, Galina I. Nevrina, Igor K. Petrushenko, Igor A. Ushakov, Anna V. Vologzhanina, Konstantin A. Lyssenko, Daria V. Berdnikova, Andrey G. Lvov. “Self-tuning of photoswitching performance for non-cyclic diarylethenes.” ChemRxiv (2026). https://doi.org/10.26434/chemrxiv.15007513/v1

4,4'-(But-2-enE-2,3-diyl)bis(5-methyl-2-phenyloxazole
Identifier	1
Melting point, Z-isomer	105–107 °C
Z-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 8.01–7.94 (m, 4H), 7.47–7.36 (m, 6H), 2.19 (s, 6H), 1.86 (s, 6H)
E-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 8.08–8.01 (m, 4H), 7.49–7.37 (m, 6H), 2.37 (s, 6H), 2.01 (s, 6H)
E-isomer, ¹³C NMR (101 MHz, CDCl₃)	δ = 159.67 (2C), 143.94 (2C), 137.66 (2C), 129.92 (2C), 128.78 (4C), 128.00 (2C), 126.98 (2C), 126.19 (4C), 20.37 (2C), 11.63 (2C)
HRMS (ESI), m/z [M + H]⁺	Calculated for C₂₄H₂₃N₂O₂ 371.1760, found 371.1763

4,4'-(But-2-enE-2,3-diyl)bis(2-(4-methoxyphenyl)-5-methyloxazole)
Identifier	3
Melting point, Z-isomer	190–193 °C
Z-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 7.92 (d, J = 7.5 Hz, 4H), 6.95 (d, J = 7.5 Hz, 4H), 3.85 (s, 6H), 2.17 (s, 6H), 1.84 (s, 6H)
E-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 7.97 (d, J = 9.0 Hz, 4H), 6.96 (d, J = 9.0 Hz, 4H), 3.86 (s, 6H), 2.33 (s, 6H), 1.99 (s, 6H)
Z-isomer, ¹³C NMR (101 MHz, CDCl₃)	δ = 161.05 (2C), 159.51 (2C), 143.35 (2C), 137.86 (2C), 127.72 (4C), 126.87 (2C), 120.84 (2C), 114.22 (4C), 55.52 (2C), 19.16 (2C), 10.95 (2C)
HRMS (ESI), m/z [M + H]⁺	Calcd for C₂₆H₂₇N₂O₄: 431.1970, found: 431.1975

4,4'-(But-2-enE-2,3-diyl)bis(5-methyl-2-(p-tolyl)oxazole)
Identifier	2
Melting point, E-isomer	175–177 °C
Z-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 7.87 (d, J = 8.3 Hz, 4H), 7.28–7.23 (m, 4H), 2.38 (s, 6H), 2.18 (s, 6H), 1.85 (s, 6H)
E-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 7.92 (d, J = 7.9 Hz, 4H), 7.25–7.22 (m, 4H), 2.40 (s, 6H), 2.35 (s, 6H), 2.00 (s, 6H)
Mixture of E/Z-isomers, ¹³C NMR (101 MHz, CDCl₃)	δ = 159.84, 159.61, 143.59, 143.51, 140.03, 139.96, 137.99, 137.48, 129.46, 126.92, 126.85, 126.84, 126.13, 126.02, 125.32, 125.23, 21.59, 21.55, 20.36, 19.13, 11.60, 10.92
HRMS (ESI), m/z [M + H]⁺	Calculated for C₂₆H₂₇N₂O₂: 399.2060, found: 399.2073

4,4'-(But-2-enE-2,3-diyl)bis(2-(4-fluorophenyl)-5-methyloxazole)
Identifier	4
Melting point, Z-isomer	130–132 °C
Z-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 8.02–7.92 (m, 4H), 7.17–7.07 (m, 4H), 2.17 (s, 6H), 1.86 (s, 6H)
E-isomer, ¹H NMR (400 MHz, CDCl₃)	8.06–8.00 (m, 4H), 7.17–7.07 (m, 4H), 2.35 (s, 6H), 1.99 (s, 6H)
Z-isomer, ¹³C NMR (101 MHz, CDCl₃)	δ = 165.10 (1C), 162.62 (1C), 158.68 (2C), 144.01 (2C), 138.19 (2C), 128.12 (d, J = 8.5 Hz, 4C), 126.93 (2C), 124.27 (2C), 115.94 (d, J = 22.1 Hz, 4C), 19.14 (2C), 10.97 (2C)
HRMS (ESI), m/z [M + H]⁺	Calculated for C₂₄H₂₁F₂N₂O₂: 407.1565, found; 407.1572

4,4'-(But-2-enE-2,3-diyl)bis(2-(3,5-bis(trifluoromethyl)phenyl)-5-methyloxazole)
Identifier	5
Melting point, Z-isomer	127–130 °C
Z-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 8.40 (s, 4H), 7.89 (s, 2H), 2.20 (s, 6H), 1.93 (s, 6H)
E-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 8.48 (s, 4H), 7.91 (s, 2H), 2.42 (s, 6H), 2.01 (s, 6H)
Z-isomer, ¹³C NMR (101 MHz, CDCl₃)	δ = 156.86 (2C), 145.66 (2C), 139.06 (2C), 132.56 (q, J = 33.8 Hz, 4C), 129.56 (2C), 127.26 (2C), 125.90 (m, 4C), 124.55 (2C), 123.34–122.87 (m, 2C), 121.84 (2C), 19.14 (2C), 11.10 (2C)
HRMS (ESI), m/z [M + H]⁺	Calculated for C₂₈H₁₉F₁₂N₂O₂ 643.1249, found 643.1250

4,4'-((But-2-enE-2,3-diylbis(5-methyloxazolE-4,2-diyl))bis(4,1-phenylene))dimorpholine
Identifier	6
Melting point, Z-isomer	190–193 °C
Z-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 7.87 (d, J = 9.1 Hz, 4H), 6.92 (d, J = 8.6 Hz, 4H), 3.89–3.85 (m, 8H), 3.25–3.22 (m, 8H), 2.16 (s, 6H), 1.83 (s, 6H)
E-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 7.93 (d, J = 9.0 Hz, 4H), 6.95–6.91 (m, 4H), 3.91–3.84 (m, 4H), 3.26–3.22 (m, 4H), 2.33 (s, 6H), 1.99 (s, 6H)
Z-isomer, ¹³C NMR (101 MHz, CDCl₃)	δ = 159.63 (2C), 152.18 (2C), 143.03 (2C), 137.79 (2C), 127.30 (4C), 126.80 (2C), 119.30 (2C), 114.91 (4C), 66.86 (4C), 48.60 (4C), 19.14 (2C), 10.93 (2C)
HRMS (ESI), m/z [M + H]⁺	Calculated for C₃₂H₃₇N₄O₄: 541.2809, found: 541.2815

4-(4-(4-(3-(2-(3,5-bis(trifluoromethyl)phenyl)-5-methyloxazol-4-yl)but-2-en-2-yl)-5-methyloxazol-2-yl)phenyl)morpholine
Identifier	7
Melting point, Z-isomer	125–127 °C
Z-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 8.41 (s, 2H), 7.88–7.85 (m, 3H), 6.92 (d, J = 9.0 Hz, 2H), 3.87 (t, J = 4.9 Hz, 4H), 3.24 (t, J = 4.9 Hz, 4H), 2.19–2.15 (m, 6H), 1.90 (s, 3H), 1.85 (s, 3H)
E-isomer, ¹H NMR (400 MHz, CDCl₃)	δ = 8.47 (s, 2H), 7.98–7.88 (m, 3H), 6.98–6.90 (m, 2H), 3.87 (m, 4H), 3.24 (m, 4H), 2.40 (s, 3H), 2.34 (s, 3H), 2.03–1.97 (m, 6H)
Mixture of E/Z-isomers, ¹³C NMR (101 MHz, CDCl₃)	δ = 160.07, 159.89, 156.92, 156.61, 152.33, 152.29, 145.77, 145.58, 143.12, 142.92, 139.21, 138.64, 137.62, 136.97, 132.45 (q, J = 33.8 Hz, 2C), 129.88, 129.69, 128.05, 128.00, 127.47, 127.34, 126.03, 125.87, 124.58, 123.02, 122.88, 121.86, 119.20, 119.03, 114.88, 66.85, 48.61, 48.54, 20.37, 20.34, 19.23, 19.03, 11.67, 11.61, 11.07, 10.95
HRMS (ESI), m/z [M + H]⁺	Calculated for C₃₀H₂₈F₆N₃O₃: 592.2029, found: 592.2034

N1,N4-diacetyl-N1,N4-dibenzoyl-2,3-dimethylbut-2-enediamide
Identifier	8a
Melting point	125–122 °C
¹H NMR (400 MHz, CDCl₃)	7.76 (d, J = 8.1 Hz, 4H), 7.61 (t, J = 7.5 Hz, 2H), 7.46 (t, J = 7.8 Hz, 4H), 2.43 (s, 6H), 1.92 (s, 6H)
¹³C NMR (101 MHz, CDCl₃)	172.49 (2C), 171.30 (2C), 171.29 (2C), 134.59 (2C), 134.18 (4C), 132.70 (2C), 130.01 (4C), 129.15 (4C), 25.94 (2C), 17.74 (2C)
HRMS (ESI), m/z	Calculated for [C₂₄H₂₄N₂O₇, M + H₂O]: 452.1936, found: 452.1815
MS (EI), m/z (%)	350 (5, [M-OAc-OAc+2H]⁺), 105 (100, [C(O)OAr]⁺)

N1,N4-diacetyl-2,3-dimethyl-N1,N4-bis(4-methylbenzoyl)but-2-enediamide
Identifier	8b
Melting point	80–83 °C
¹H NMR (400 MHz, CDCl₃)	7.68 (d, J = 7.9 Hz, 4H), 7.27–7.22 (m, 4H), 2.42 (s, 6H), 2.42 (s, 6H), 1.90 (s, 6H)
¹³C NMR (101 MHz, CDCl₃)	172.44 (2C), 171.36 (2C), 170.98 (2C), 145.96 (2C), 134.03 (2C), 130.30 (4C), 130.09 (2C), 129.90 (4C), 25.96 (2C), 21.95 (2C), 17.78 (2C)
HRMS (ESI), m/z	Calculated for [C₂₆H₂₆N₂O₇, M + H₂O]: 480.1897, found: 480.1924
MS (EI), m/z (%)	378 (2, [M-OAc-OAc+2H]⁺), 216 (20), 119 (100, [C(O)Ar]⁺)

N1,N4-diacetyl-N1,N4-bis(4-methoxybenzoyl)-2,3-dimethylbut-2-enediamide
Identifier	8c
Melting point	105–109 °C
¹H NMR (400 MHz, CDCl₃)	7.77 (d, J = 8.8 Hz, 4H), 6.93 (d, J = 8.7 Hz, 4H), 3.88 (s, 6H,), 2.42 (s, 6H), 1.89 (s, 6H)
¹³C NMR (101 MHz, CDCl₃)	172.27 (2C), 171.28 (2C), 170.05 (2C), 164.93 (2C), 133.79 (2C), 132.77 (4C), 125.14 (2C), 114.54 (4C), 55.78 (2C), 25.92 (2C), 17.78 (2C)
HRMS (ESI), m/z	Calculated for [C₂₆H₂₆N₂O₉, M + H₂O]: 512.1794, Found: 512.2023
MS (EI), m/z (%)	410 (2, [M-OAc-OAc+2H]⁺), 135 (100, [C(O)Ar]⁺)

N1,N4-diacetyl-N1,N4-bis(4-fluorobenzoyl)-2,3-dimethylbut-2-enediamide
Identifier	8d
Melting point	142–143 °C
¹H NMR (400 MHz, CDCl₃)	7.81–7.76 (m, 4H), 7.17–7.11 (m, 4H), 2.44 (s, 6H), 1.92 (s, 6H)
¹³C NMR (101 MHz, CDCl₃)	172.49 (2C), 171.17 (2C), 170.15 (2C), 167.91 (2C), 165.35 (2C), 134.09 (2C), 132.83 (d, J = 9.8 Hz, 4C), 129.04 (2C), 116.69 (d, J = 22.4 Hz, 2C), 26.00 (2C), 17.86 (2C)
HRMS (ESI), m/z	Calculated for C₂₄H₂₀F₂N₂O₆: 471.1362, found: 471.1371
MS (EI), m/z (%)	386 (5, [M-OAc-OAc+2H]⁺), 220 (30), 123 (100, [C(O)Ar]⁺)

N1,N4-diacetyl-2,3-dimethyl-N1,N4-bis(4-morpholinobenzoyl)but-2-enediamide
Identifier	9
Melting point	115–117 °C
¹H NMR (400 MHz, CDCl₃)	8.42 (s, 2H), 7.77 (d, J = 8.8 Hz, 4H), 6.91 (d, J = 8.9 Hz, 4H), 3.86 (t, J = 4.9 Hz, 8H), 3.32 (t, J = 4.9 Hz, 8H), 2.60 (s, 6H)
HRMS (ESI), m/z	Calculated for [C₂₈H₃₂N₄O₆ M – H]: 519.2238, found: 519.2255
MS (EI), m/z (%)	248 (75), 190 (70, [C(O)Ar]⁺), 132 (100)

Chemical shifts of methyl groups for dioxazolylbutenes 1–7 in CDCl₃
Compound 1, E-isomer	2.01, 2.37 ppm
Compound 1, Z-isomer	1.86, 2.19 ppm
Compound 1, closed-ring isomer	1.57, 2.02 ppm
Compound 2, E-isomer	2.00, 2.35 ppm
Compound 2, Z-isomer	1.85, 2.18 ppm
Compound 2, closed-ring isomer	1.56, 2.02 ppm
Compound 3, E-isomer	1.99, 2.33 ppm
Compound 3, Z-isomer	1.84, 2.17 ppm
Compound 3, closed-ring isomer	1.56, 2.02 ppm
Compound 4, E-isomer	1.99, 2.35 ppm
Compound 4, Z-isomer	1.86, 2.17 ppm
Compound 4, closed-ring isomer	1.56, 2.01 ppm
Compound 5, E-isomer	2.01, 2.42 ppm
Compound 5, Z-isomer	1.93, 2.20 ppm
Compound 5, closed-ring isomer	1.61, 2.05 ppm
Compound 6, E-isomer	1.99, 2.33 ppm
Compound 6, Z-isomer	1.83, 2.16 ppm
Compound 6, closed-ring isomer	1.55, 2.05 ppm
Compound 7, E-isomer	2.40, 2.34, 2.03, 1.97 ppm
Compound 7, Z-isomer	2.19, 2.15, 1.90, 1.85 ppm
Compound 7, closed-ring isomer	2.02, 2.00, 1.57, 1.55 ppm

Absorbance maxima and molar extinction coefficients of 1–7 in various solvents, λmax, nm (ε, 10⁻⁴ M⁻¹ cm⁻¹)
Z-1, toluene	316 (2.0)
Z-1, acetonitrile	309 (2.4)
Z-1, chloroform	–
E-2, toluene	294 (3.2)
E-2, acetonitrile	301 (3.2)
E-2, chloroform	–
Z-3, toluene	306 (3.9)
Z-3, acetonitrile	299 (3.0)
Z-3, chloroform	–
Z-4, toluene	302 (2.7)
Z-4, acetonitrile	306 (2.2)
Z-4, chloroform	–
Z-5, toluene	331 (2.3)
Z-5, acetonitrile	–
Z-5, chloroform	327 (1.1)
c-5, toluene	–
c-5, acetonitrile	–
c-5, chloroform	470 (1.21)
Z-6, toluene	335 (5.3)
Z-6, acetonitrile	335 (5.8)
Z-6, chloroform	–
Z-7, toluene	322 (3.5)
Z-7, acetonitrile	–
Z-7, chloroform	–

4,4'-(But-2-enE-2,3-diyl)bis(2-(3,5-bis(trifluoromethyl)phenyl)-5-methyloxazole), in toluene
Identifier	5
Absorption-spectra concentration	c ≈ 10⁻⁵ M
E-5 absorption maximum	ca. 320 nm
Band formed under UV irradiation, 365 nm	450–500 nm
New species absorption maximum after blue, 465 nm, or green, 512 nm, irradiation	ca. 340 nm
Z-5 quantum yield for direct cyclization	0.59
Z-5 quantum yield for cycloreversion	0.1
Thermal back isomerization	Z-5 and c-5 did not undergo thermal back isomerization to E-5 and Z-5, respectively

4,4'-(But-2-enE-2,3-diyl)bis(2-(3,5-bis(trifluoromethyl)phenyl)-5-methyloxazole), self-tuning monitored by ¹H NMR spectroscopy in CDCl₃
Identifier	5
¹H NMR conditions	c ≈ 10⁻² M, quartz tube, air; UV, λmax = 313 nm, and green light, λmax = 512 nm
Starting E-5/Z-5 mixture	1 : 1
After the first UV/VIS cycle	Pure Z-isomer

4-(4-(4-(3-(2-(3,5-bis(trifluoromethyl)phenyl)-5-methyloxazol-4-yl)but-2-en-2-yl)-5-methyloxazol-2-yl)phenyl)morpholine, self-tuning
Identifier	7
Absorption-spectra conditions	Toluene, c ≈ 10⁻⁵ M, 365 nm/465 nm irradiation
After the first UV/VIS cycle	The absorption maxima underwent slight bato- and hyperchromic shift
¹H NMR conditions	C₆D₆, c ≈ 10⁻² M, 365 nm/512 nm irradiation
E/Z-isomer content after column chromatography	≈ 1 : 4
After the first UV/green-light cycle	The mixture of E- and Z-isomers was converted into almost pure Z-isomer
Chloroform and acetonitrile	A similar effect was no longer observed

4,4'-(But-2-enE-2,3-diyl)bis(2-(4-methoxyphenyl)-5-methyloxazole)
Identifier	3
Absorption spectroscopy conditions	Toluene, c ≈ 10⁻⁵ M, UV 313 nm, visible 465 nm
After the first UV/VIS cycle	Self-tuning towards Z-3
¹H NMR conditions	CDCl₃, c ≈ 10⁻² M, borosilicate tube, air
Z-3 with gaseous hydrogen chloride in CDCl₃ under UV irradiation, 365 nm	no traces of closed-ring isomer were observed
After controllable UV irradiation, dark relaxation, and treatment with NaHCO3	Mixture of non-protonated E/Z-isomers with equal content

4-methoxyphenyl dioxazolylbutene
Identifier	2
Configuration determined by X-ray crystallography	Z-isomer

E-isomer of 4,4'-(But-2-enE-2,3-diyl)bis(5-methyl-2-phenyloxazole, crystal data and structure refinement
Identifier	E-1
Identification code	EKK114
Empirical formula	C₂₄H₂₂N₂O₂
Formula weight	370.43
Temperature/K	120
Crystal system	Orthorhombic
Space group	P212121
a/Å	10.8579(7)
b/Å	11.4296(7)
c/Å	15.2572(9)
α/°	90
β/°	90
γ/°	90
Volume/Å³	1893.4(2)
Z	4
ρcalc g/cm³	1.299
μ/mm⁻¹	0.083
F(000)	784.0
Crystal size/mm³	0.19 × 0.18 × 0.12
Radiation	MoKα (λ = 0.71073)
2Θ range for data collection/°	4.452 to 61.034
Index ranges	−10 ≤ h ≤ 15, −16 ≤ k ≤ 16, −20 ≤ l ≤ 21
Reflections collected	15565
Independent reflections	5742 [Rint = 0.0334, Rsigma = 0.0448]
Data/restraints/parameters	5742/0/257
Goodness-of-fit on F2	0.999
Final R indexes [I>=2σ (I)]	R1 = 0.0538, wR2 = 0.1241
Final R indexes [all data]	R1 = 0.0670, wR2 = 0.1294
Largest diff. peak/hole / e Å⁻³	0.74/−0.25
Flack parameter	0.3(6)

Z-isomer of 4,4'-(But-2-enE-2,3-diyl)bis(2-(4-methoxyphenyl)-5-methyloxazole), crystal data and structure refinement
Identifier	Z-3
Identification code	EKK149
Empirical formula	C₂₆H₂₆N₂O₄
Formula weight	430.49
Temperature/K	120
Crystal system	Orthorhombic
Space group	Pbcn
a/Å	11.1806(4)
b/Å	7.7401(3)
c/Å	24.6861(8)
α/°	90
β/°	90
γ/°	90
Volume/Å³	2136.31(13)
Z	4
ρcalc g/cm³	1.338
μ/mm⁻¹	0.091
F(000)	912.0
Crystal size/mm³	0.25 × 0.21 × 0.06
Radiation	MoKα (λ = 0.71073)
2Θ range for data collection/°	3.3 to 61.112
Index ranges	−15 ≤ h ≤ 15, −11 ≤ k ≤ 8, −32 ≤ l ≤ 35
Reflections collected	17720
Independent reflections	3252 [Rint = 0.0339, Rsigma = 0.0320]
Data/restraints/parameters	3252/0/148
Goodness-of-fit on F2	1.055
Final R indexes [I>=2σ (I)]	R1 = 0.0411, wR2 = 0.0980
Final R indexes [all data]	R1 = 0.0549, wR2 = 0.1030
Largest diff. peak/hole / e Å⁻³	0.34/−0.33

Z-isomer of 4,4'-(But-2-enE-2,3-diyl)bis(2-(4-fluorophenyl)-5-methyloxazole), crystal data and structure refinement
Identifier	Z-4
Identification code	EKK169_pxrd
Empirical formula	C₂₄H₂₀F₂N₂O₂
Formula weight	406.42
Temperature/K	298
Crystal system	Monoclinic
Space group	P21/c
a/Å	21.5381(5)
b/Å	7.34804(13)
c/Å	13.6787(3)
α/°	90
β/°	102.4515(10)
γ/°	90
Volume/Å³	2113.910
Z	4
μ/mm⁻¹	0.094
F(000)	848.0
Radiation	CuKα1 (λ = 1.540596)
2Θ range for data collection/°	6 to 80
Goodness-of-fit on F2	0.01808
Final R indexes	Rp = 0.01448, Rwp = 0.02044, Rwp′ = 0.01885, RBragg = 0.01131

Z-isomer of 4,4'-(But-2-enE-2,3-diyl)bis(2-(3,5-bis(trifluoromethyl)phenyl)-5-methyloxazole), crystal data and structure refinement
Identifier	Z-5
Identification code	EKK84
Empirical formula	C₂₈H₁₈F₁₂N₂O₂
Formula weight	642.44
Temperature/K	100
Crystal system	Monoclinic
Space group	C2/c
a/Å	16.991(3)
b/Å	15.303(3)
c/Å	12.1440(19)
α/°	90
β/°	106.523(7)
γ/°	90
Volume/Å³	3027.3(9)
Z	8
μ/mm⁻¹	0.139
F(000)	1296.0
Radiation	MoKα (λ = 0.71073)
2Θ range for data collection/°	4.538 to 57.998
Goodness-of-fit on F2	1.038
Final R indexes [I>=2σ (I)]	R1 = 0.0637, wR2 = 0.1668