Electron diffraction and solid-state NMR reveal the structure and exciton coupling in a eumelanin precursor.
Vinod, Kavya; Mathew, Renny; Jandl, Christian; Thomas, Brijith; Hariharan, Mahesh; Chemical science 15 (2024) 16015–16024; doi:10.1039/d4sc05453a

data_1573017
_publ_section_title
;
 Electron diffraction and solid-state NMR reveal the structure and exciton
 coupling in a eumelanin precursor.
;
_journal_issue                   39
_journal_name_full               'Chemical science'
_journal_page_first              16015
_journal_page_last               16024
_journal_paper_doi               10.1039/d4sc05453a
_journal_volume                  15
_journal_year                    2024
_chemical_compound_source        'see text'
_chemical_formula_moiety         'C9 H7 N O4'
_chemical_formula_sum            'C9 H7 N O4'
_chemical_formula_weight         193.16
_space_group_IT_number           2
_space_group_name_Hall           '-P 1'
_space_group_name_H-M_alt        'P -1'
_symmetry_cell_setting           triclinic
_symmetry_Int_Tables_number      2
_symmetry_space_group_name_Hall  '-P 1'
_symmetry_space_group_name_H-M   'P -1'
_atom_sites_solution_hydrogens   mixed
_atom_sites_solution_primary     XT
_atom_sites_solution_secondary   difmap
_audit_update_record
;
2024-05-29 deposited with the CCDC.	2024-09-16 downloaded from the CCDC.
;
_cell_angle_alpha                82.27(3)
_cell_angle_beta                 87.799(13)
_cell_angle_gamma                70.095(13)
_cell_formula_units_Z            4
_cell_length_a                   7.49(7)
_cell_length_b                   10.23(9)
_cell_length_c                   10.81(10)
_cell_measurement_reflns_used    156
_cell_measurement_temperature    298
_cell_measurement_theta_max      0.8142
_cell_measurement_theta_min      0.2916
_cell_volume                     772(12)
_computing_cell_refinement       'SAINT (Bruker 2019)'
_computing_data_collection       'Eldix (ELDICO 2023)'
_computing_data_reduction        'SAINT (Bruker 2019)'
_computing_molecular_graphics    'Mercury (Macrae 2008)'
_computing_publication_material  'EnCIFer (Allen 2004), PLATON (Spek 2009)'
_computing_structure_refinement
'SHELXL (Sheldrick 2015), ShelXle (Huebschle 2011)'
_computing_structure_solution    'SHELXT (Sheldrick 2015)'
_diffrn_ambient_temperature      298
_diffrn_detector                 'Dectris QUADRO'
_diffrn_detector_area_resol_mean 13.33
_diffrn_measured_fraction_theta_full 0.971
_diffrn_measured_fraction_theta_max 0.969
_diffrn_measurement_device       'ELDICO ED-1'
_diffrn_measurement_device_type  'electron diffractometer'
_diffrn_measurement_method       'continuous rotation 3D ED'
_diffrn_radiation_source         LaB~6~
_diffrn_radiation_type           electron
_diffrn_radiation_wavelength     0.02851
_diffrn_reflns_av_R_equivalents  0.1488
_diffrn_reflns_av_unetI/netI     0.1551
_diffrn_reflns_limit_h_max       9
_diffrn_reflns_limit_h_min       -8
_diffrn_reflns_limit_k_max       12
_diffrn_reflns_limit_k_min       -11
_diffrn_reflns_limit_l_max       12
_diffrn_reflns_limit_l_min       -12
_diffrn_reflns_number            7939
_diffrn_reflns_reduction_process
;
;
_diffrn_reflns_theta_full        0.98
_diffrn_reflns_theta_max         0.98
_diffrn_reflns_theta_min         0.08
_exptl_absorpt_correction_T_max  0.7431
_exptl_absorpt_correction_T_min  0.3575
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   'SADABS 2016/2 (Bruker 2016)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.660
_exptl_crystal_density_method    'Not Measured'
_exptl_crystal_description       nanocrystals
_exptl_crystal_F_000             0
_refine_diff_density_max         0.219
_refine_diff_density_min         -0.258
_refine_diff_density_rms         0.051
_refine_ls_extinction_coef       1996(21)
_refine_ls_extinction_expression FC^*^=KFC[1+0.001XFC^2^\L^3^/SIN(2\Q)]^-1/4^
_refine_ls_extinction_method     'shelxl-2019/1 (sheldrick 2015)'
_refine_ls_goodness_of_fit_ref   1.088
_refine_ls_hydrogen_treatment    mixed
_refine_ls_matrix_type           full
_refine_ls_number_parameters     264
_refine_ls_number_reflns         2729
_refine_ls_number_restraints     2
_refine_ls_restrained_S_all      1.088
_refine_ls_R_factor_all          0.1880
_refine_ls_R_factor_gt           0.1365
_refine_ls_shift/su_max          0.099
_refine_ls_shift/su_mean         0.001
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'W=1/[\S^2^(FO^2^)+(0.1448P)^2^+0.3234P] WHERE P=(FO^2^+2FC^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.3234
_refine_ls_wR_factor_ref         0.3604
_reflns_number_gt                1582
_reflns_number_total             2729
_reflns_threshold_expression     I>2\s(I)
_cod_data_source_file            d4sc05453a2.cif
_cod_data_source_block           I
_cod_database_code               1573017
_shelx_res_checksum              96270
_shelx_hkl_checksum              98791