Maleic acid + 1-methylimidazole
Callear, Samantha K.; Hursthouse, Michael B.; Crystal Structure Report Archive  (2008) 523–; doi:

data_1520174
_publ_section_title
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 Maleic acid + 1-methylimidazole
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_journal_name_full               'Crystal Structure Report Archive'
_journal_page_first              523
_journal_year                    2008
_chemical_formula_sum            'C8 H10 N2 O4'
_chemical_formula_weight         198.18
_chemical_name_systematic
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maleic acid and 1-methylimidazole
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_space_group_IT_number           19
_symmetry_cell_setting           orthorhombic
_symmetry_space_group_name_Hall  'P 2ac 2ab'
_symmetry_space_group_name_H-M   'P 21 21 21'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_cell_angle_alpha                90.00
_cell_angle_beta                 90.00
_cell_angle_gamma                90.00
_cell_formula_units_Z            4
_cell_length_a                   7.7110(2)
_cell_length_b                   8.2850(4)
_cell_length_c                   13.8440(5)
_cell_measurement_reflns_used    5426
_cell_measurement_temperature    120(2)
_cell_measurement_theta_max      28.60
_cell_measurement_theta_min      2.70
_cell_volume                     884.43(6)
_computing_cell_refinement       'Bruker SAINT'
_computing_data_collection       'Bruker APEX2'
_computing_data_reduction        'Bruker SAINT'
_computing_structure_refinement  'SHELXL-97 (Sheldrick, 1997)'
_diffrn_ambient_temperature      120(2)
_diffrn_measured_fraction_theta_full 0.965
_diffrn_measured_fraction_theta_max 0.965
_diffrn_measurement_device_type  'Bruker SMART APEX2 CCD diffractometer'
_diffrn_measurement_method       'fine-slice \w scans'
_diffrn_radiation_monochromator  'silicon 111'
_diffrn_radiation_source         'Daresbury SRS station 9.8'
_diffrn_radiation_type           synchrotron
_diffrn_radiation_wavelength     0.6710
_diffrn_reflns_av_R_equivalents  0.0556
_diffrn_reflns_av_sigmaI/netI    0.0335
_diffrn_reflns_limit_h_max       10
_diffrn_reflns_limit_h_min       -9
_diffrn_reflns_limit_k_max       10
_diffrn_reflns_limit_k_min       -10
_diffrn_reflns_limit_l_max       17
_diffrn_reflns_limit_l_min       -17
_diffrn_reflns_number            7597
_diffrn_reflns_theta_full        27.48
_diffrn_reflns_theta_max         27.48
_diffrn_reflns_theta_min         5.71
_diffrn_standards_decay_%        5
_diffrn_standards_number         0
_exptl_absorpt_coefficient_mu    0.121
_exptl_absorpt_correction_T_max  0.9880
_exptl_absorpt_correction_T_min  0.9833
_exptl_absorpt_correction_type   none
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.488
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       block
_exptl_crystal_F_000             416
_exptl_crystal_size_max          0.14
_exptl_crystal_size_mid          0.10
_exptl_crystal_size_min          0.10
_refine_diff_density_max         0.426
_refine_diff_density_min         -0.231
_refine_diff_density_rms         0.060
_refine_ls_abs_structure_details 'Flack H D (1983), Acta Cryst. A39, 876-881'
_refine_ls_abs_structure_Flack   -10(10)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   1.158
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     129
_refine_ls_number_reflns         1145
_refine_ls_number_restraints     0
_refine_ls_restrained_S_all      1.158
_refine_ls_R_factor_all          0.0637
_refine_ls_R_factor_gt           0.0627
_refine_ls_shift/su_max          0.002
_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.0690P)^2^+1.1643P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1723
_refine_ls_wR_factor_ref         0.1728
_reflns_number_gt                1118
_reflns_number_total             1145
_reflns_threshold_expression     >2sigma(I)
_cod_data_source_file            eCrystal-523.cif
_cod_data_source_block           ssg0301
_cod_depositor_comments
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Citation :
Callear, Samantha K. and Hursthouse, Michael B. and National 
Crystallography Service, (2008) 
University of Southampton, Crystal Structure Report Archive. 
(doi:10.5258/ecrystals/523)

More at:
http://ecrystals.chem.soton.ac.uk/523/
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_cod_original_sg_symbol_H-M      P212121
_cod_database_code               1520174