A time-resolved powder diffraction study of in-situ photodimerization kinetics of 9-methylanthracene using a CCD area detector and parametric Rietveld refinement

The [4π + 4π] photodimerization process of the 9-substituted anthracene derivative crystalline 9-methylanthracene (9-MA) was investigated using time-resolved X-ray powder diffraction. The study was carried out in-situ using a CCD area detector. Sequential and parametric Rietveld refinement was applied for quantitative phase analysis. The results of traditional sequential Rietveld refinement showed that the evolution of the dimerization process can be described using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. The parameters of the JMAK equation were obtained successfully by parametric Rietveld refinement and suggest that the reaction follows heterogeneous nucleation and one-dimensional growth with a decreasing nucleation rate.

Computing details

(9mai_phase_1)

Crystal data

C15H12	α = 90°
Mr = 192.25	β = 96.95 (3)°
P21/c	γ = 90°
a = 8.679 (3) Å	V = 995.8 (5) Å^3
b = 14.402 (3) Å	Z = 4
c = 8.026 (2) Å

Data collection

MarDTB NW14A beamline diffractometer

Scan method: Stationary detector

Refinement

Rexp = 10.133

1707 data points

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
C1	0.52341	0.67391	−0.63768	5.061133
C2	0.34886	0.58867	−0.40048	6.016511
C3	0.28187	0.61433	−0.55182	6.008615
C4	0.37155	0.65817	−0.67376	5.045342
C5	0.29169	0.68454	−0.83685	4.768993
C6	0.13995	0.66876	−0.87299	5.637518
C7	0.04945	0.62468	−0.75006	5.598040
C8	0.11635	0.59896	−0.59875	4.792680
C9	0.60258	0.64741	−0.47441	3.837302
C10	0.51403	0.60419	−0.35414	4.074173
C11	0.58307	0.57906	−0.20373	3.782032
C12	0.74955	0.59537	−0.16014	3.947842
C13	0.83113	0.63516	−0.27097	3.758345
C14	0.75406	0.66246	−0.43603	3.608327
C15	0.25377	0.54390	−0.27803	5.755953
H16	0.58266	0.70385	−0.72263	6.790288
H17	0.35073	0.71454	−0.92194	7.500899
H18	0.08639	0.68713	−0.98552	6.395504
H19	−0.06425	0.61391	−0.78089	6.316547
H20	0.05293	0.56911	−0.51749	4.737410
H21	0.52145	0.54915	−0.12085	6.711331
H22	0.80194	0.57666	−0.04729	7.579856
H23	0.94487	0.64637	−0.24148	6.000720
H24	0.81494	0.69231	−0.51964	4.421583
H25	0.32188	0.52926	−0.17171	4.537537
H26	0.20651	0.48526	−0.32756	5.723456
H27	0.16959	0.58734	−0.25325	4.162410

(9mai_phase_2)

Crystal data

C30H24	α = 90°
Mr = 384.49	β = 115.14 (2)°
P21/c	γ = 90°
a = 9.851 (2) Å	V = 963.2 (4) Å^3
b = 13.285 (3) Å	Z = 2
c = 8.1301 (17) Å

Data collection

MarDTB NW14A beamline diffractometer

Scan method: Stationary detector

Refinement

Rexp = 10.133

1707 data points

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
C1	−0.69995	0.20518	−0.12917	4.271565
C2	−0.84073	0.21201	−0.13154	4.808471
C3	−0.88785	0.14246	−0.04275	4.682140
C4	−0.79194	0.06565	0.05367	4.208399
C5	−0.29688	−0.00003	0.44253	4.208399
C6	−0.15899	0.04597	0.52933	4.958489
C7	−0.11086	0.11372	0.43910	4.642662
C8	−0.20228	0.13722	0.25815	3.955737
C9	−0.54261	−0.11867	0.03867	3.371457
C10	−0.54094	−0.02335	0.16455	3.529371
C11	−0.60314	0.12852	−0.03518	3.576745
C12	−0.64969	0.05881	0.05918	3.489892
C13	−0.38853	0.02324	0.26380	3.474101
C14	−0.34087	0.09297	0.16995	3.434622
C15	−0.60050	−0.20748	0.11055	4.555809
H1	−0.67300	0.25221	−0.19580	6.158633
H2	−0.91249	0.26827	−0.21096	5.132194
H3	−0.99243	0.14901	−0.04173	6.474461
H4	−0.81805	0.00966	0.12188	6.079676
H5	−0.33589	−0.05533	0.50623	4.737410
H6	−0.08859	0.03207	0.65112	5.448022
H7	−0.00903	0.15009	0.50113	5.763849
H8	−0.17345	0.19186	0.18657	3.868885
H10	−0.57478	−0.05518	0.25875	3.789928
H15A	−0.52961	−0.21912	0.24415	4.974281
H15B	−0.72132	−0.19136	0.09339	6.711331
H15C	−0.61189	−0.27147	0.03531	7.185072