Polymorphs of anhydrous theophylline: stable form IV consists of dimer pairs and metastable form I consists of hydrogen-bonded chains
Khamar, Dikshitkumar; Pritchard, Robin Gavin; Bradshaw, Ian James; Hutcheon, Gillian Ann; Seton, Linda; Acta Crystallographica Section C 67 (2011) o496–o499; doi:10.1107/S010827011104786X

data_2018308
_publ_section_title
;
 Polymorphs of anhydrous theophylline: stable form IV consists of dimer
 pairs and metastable form I consists of hydrogen-bonded chains
;
_journal_coeditor_code           BM3111
_journal_issue                   12
_journal_name_full               'Acta Crystallographica Section C'
_journal_page_first              o496
_journal_page_last               o499
_journal_paper_doi               10.1107/S010827011104786X
_journal_volume                  67
_journal_year                    2011
_chemical_formula_iupac          'C7 H8 N4 O2'
_chemical_formula_moiety         'C7 H8 N4 O2'
_chemical_formula_sum            'C7 H8 N4 O2'
_chemical_formula_weight         180.17
_chemical_name_systematic
;
3,7-dihydro-1,3-dimethyl-1<i>H</i>-purine-2,6-dione
;
_space_group_IT_number           33
_symmetry_cell_setting           orthorhombic
_symmetry_space_group_name_Hall  'P 2c -2n'
_symmetry_space_group_name_H-M   'P n a 21'
_atom_sites_solution_hydrogens   geom
_atom_sites_solution_primary     direct
_atom_sites_solution_secondary   difmap
_audit_conform_dict_name         cif_core.dic
_audit_conform_dict_version      2.4
_audit_creation_method           'WinGX routine CIF_UPDATE'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   13.158(2)
_cell_length_b                   15.630(3)
_cell_length_c                   3.8540(10)
_cell_measurement_reflns_used    817
_cell_measurement_temperature    100(2)
_cell_measurement_theta_max      26
_cell_measurement_theta_min      2
_cell_volume                     792.6(3)
_computing_cell_refinement       'HKL SCALEPACK (Otwinowski & Minor, 1997)'
_computing_data_collection       'COLLECT (Hooft, 1998)'
_computing_data_reduction
'HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997)'
_computing_molecular_graphics    'ORTEP-3 for Windows (Farrugia, 1997)'
_computing_publication_material  'WinGX publication routines (Farrugia, 1999)'
_computing_structure_refinement  'SHELXL97 (Sheldrick, 2008)'
_computing_structure_solution    'SIR92 (Altomare <i>et al.</i>, 1994)'
_diffrn_ambient_temperature      100(2)
_diffrn_detector_area_resol_mean 9
_diffrn_measured_fraction_theta_full 0.902
_diffrn_measured_fraction_theta_max 0.902
_diffrn_measurement_device       '95mm CCD camera on \k-goniostat'
_diffrn_measurement_device_type  'Nonius KappaCCD area-detector'
_diffrn_measurement_method       'CCD rotation images, thick slices'
_diffrn_radiation_monochromator  graphite
_diffrn_radiation_type           MoK\a
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0398
_diffrn_reflns_limit_h_max       15
_diffrn_reflns_limit_h_min       -15
_diffrn_reflns_limit_k_max       18
_diffrn_reflns_limit_k_min       -18
_diffrn_reflns_limit_l_max       4
_diffrn_reflns_limit_l_min       -4
_diffrn_reflns_number            1246
_diffrn_reflns_reduction_process
;
 Scaled and merged with Sortav
 R.H. Blessing, (1987) Cryst. Rev. 1, 3-58
 R.H. Blessing, (1989) J. Appl. Cryst. 22, 396-397
;
_diffrn_reflns_theta_full        25.39
_diffrn_reflns_theta_max         25.39
_diffrn_reflns_theta_min         3.1
_exptl_absorpt_coefficient_mu    0.116
_exptl_absorpt_correction_T_max  0.9965
_exptl_absorpt_correction_T_min  0.9717
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details   '(SORTAV; Blessing, 1989)'
_exptl_crystal_colour            colourless
_exptl_crystal_density_diffrn    1.51
_exptl_crystal_density_method    'not measured'
_exptl_crystal_description       prism
_exptl_crystal_F_000             376
_exptl_crystal_size_max          0.25
_exptl_crystal_size_mid          0.06
_exptl_crystal_size_min          0.03
_refine_diff_density_max         0.34
_refine_diff_density_min         -0.30
_refine_ls_abs_structure_details 'Flack (1983), no. Friedel pairs?'
_refine_ls_abs_structure_Flack   -10(10)
_refine_ls_extinction_method     none
_refine_ls_goodness_of_fit_ref   0.98
_refine_ls_hydrogen_treatment    constr
_refine_ls_matrix_type           full
_refine_ls_number_parameters     120
_refine_ls_number_reflns         764
_refine_ls_number_restraints     1
_refine_ls_restrained_S_all      0.979
_refine_ls_R_factor_all          0.1411
_refine_ls_R_factor_gt           0.0881
_refine_ls_shift/su_max          0.005
_refine_ls_shift/su_mean         0
_refine_ls_structure_factor_coef Fsqd
_refine_ls_weighting_details
'calc w=1/[\s^2^(Fo^2^)+(0.010P)^2^+3.500P] where P=(Fo^2^+2Fc^2^)/3'
_refine_ls_weighting_scheme      calc
_refine_ls_wR_factor_gt          0.1726
_refine_ls_wR_factor_ref         0.2022
_reflns_number_gt                462
_reflns_number_total             764
_reflns_threshold_expression     >2\s(I)
_cod_data_source_file            bm3111.cif
_cod_data_source_block           I
_cod_database_code               2018308
_cod_database_fobs_code          2018308