Revision of the crystal structure of `bis(glycine) squaric acid'
Seidel, Rüdiger W.; IUCrData 3 (2018) x181324–; doi:10.1107/S241431461801324X

data_1549979
_publ_section_title
;
 Revision of the crystal structure of `bis(glycine) squaric acid'
;
_journal_coeditor_code           WM5461
_journal_issue                   9
_journal_name_full               IUCrData
_journal_page_first              x181324
_journal_paper_doi               10.1107/S241431461801324X
_journal_volume                  3
_journal_year                    2018
_chemical_formula_iupac          'C4 O4, 2C2 H6 N O2'
_chemical_formula_moiety         'C4 O4, 2(C2 H6 N O2)'
_chemical_formula_sum            'C8 H12 N2 O8'
_chemical_formula_weight         264.20
_chemical_name_common            'diglycinium squarate'
_chemical_name_systematic
;
Bis(carboxymethanaminium) 3,4-dioxocyclobut-1-ene-1,2-diolate
;
_space_group_crystal_system      monoclinic
_space_group_IT_number           15
_space_group_name_Hall           '-C 2yc'
_space_group_name_H-M_alt        'C 1 2/c 1'
_symmetry_space_group_name_Hall  '-C 2yc'
_symmetry_space_group_name_H-M   'C 1 2/c 1'
_atom_sites_solution_hydrogens   mixed
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_creation_method           SHELXL-2018/3
_cell_angle_alpha                90
_cell_angle_beta                 100.259(9)
_cell_angle_gamma                90
_cell_formula_units_Z            8
_cell_length_a                   16.8050(16)
_cell_length_b                   8.3008(8)
_cell_length_c                   15.7976(13)
_cell_measurement_reflns_used    2994
_cell_measurement_temperature    293(2)
_cell_measurement_theta_max      29.3750
_cell_measurement_theta_min      3.6230
_cell_volume                     2168.5(3)
_computing_cell_refinement
;
CrysAlisPro (Rigaku OD, 2014)
;
_computing_data_collection
;
CrysAlisPro (Rigaku OD, 2014)
;
_computing_data_reduction
;
CrysAlisPro (Rigaku OD, 2014)
;
_computing_molecular_graphics
;
<i>shelXle</i> (H\"ubschle <i>et al.</i>,  2011) and DIAMOND
(Brandenburg, 2014)
;
_computing_publication_material
;
enCIFer (Allen <i>et al.</i>,  2004) and publCIF (Westrip, 2010)
;
_computing_structure_refinement
;
<i>SHELXL2018/3</i> (Sheldrick, 2015b)
;
_computing_structure_solution
;
<i>SHELXT2018/3</i> (Sheldrick, 2015a)
;
_diffrn_ambient_temperature      293(2)
_diffrn_detector_area_resol_mean 15.9853
_diffrn_measured_fraction_theta_full 0.989
_diffrn_measured_fraction_theta_max 0.852
_diffrn_measurement_device_type
'Rigaku Oxford Diffraction Xcalibur, Sapphire3'
_diffrn_measurement_method       '\w scans'
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0355
_diffrn_reflns_av_unetI/netI     0.0306
_diffrn_reflns_limit_h_max       22
_diffrn_reflns_limit_h_min       -21
_diffrn_reflns_limit_k_max       11
_diffrn_reflns_limit_k_min       -10
_diffrn_reflns_limit_l_max       19
_diffrn_reflns_limit_l_min       -21
_diffrn_reflns_number            7067
_diffrn_reflns_theta_full        25.242
_diffrn_reflns_theta_max         29.483
_diffrn_reflns_theta_min         3.642
_diffrn_source                   'Enhance (Mo) X-ray Source'
_exptl_absorpt_coefficient_mu    0.147
_exptl_absorpt_correction_T_max  1.00000
_exptl_absorpt_correction_T_min  0.40281
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details
;
(ABSPACK in CrysAlisPro; Rigaku OD, 2014)
;
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.619
_exptl_crystal_description       prism
_exptl_crystal_F_000             1104
_exptl_crystal_size_max          0.500
_exptl_crystal_size_mid          0.500
_exptl_crystal_size_min          0.500
_refine_diff_density_max         0.352
_refine_diff_density_min         -0.280
_refine_ls_extinction_coef       0.0281(16)
_refine_ls_extinction_expression Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^
_refine_ls_extinction_method
;
SHELXL-2018/3 (Sheldrick 2015b)
;
_refine_ls_goodness_of_fit_ref   1.041
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     168
_refine_ls_number_reflns         2570
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.041
_refine_ls_R_factor_all          0.0479
_refine_ls_R_factor_gt           0.0426
_refine_ls_shift/su_max          0.001
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'w=1/[\s^2^(Fo^2^)+(0.0597P)^2^+1.3230P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1090
_refine_ls_wR_factor_ref         0.1131
_reflns_number_gt                2277
_reflns_number_total             2570
_reflns_threshold_expression     'I > 2\s(I)'
_cod_data_source_file            wm5461sup1.cif
_cod_data_source_block           I
_cod_database_code               1549979
_shelx_estimated_absorpt_t_min   0.930
_shelx_estimated_absorpt_t_max   0.930
_shelx_hkl_checksum              84524
_shelx_res_checksum              61116
_cod_database_fobs_code 1549979