Protonated nucleobases are not fully ionized in their chloride salt crystals and form metastable base pairs further stabilized by the surrounding anions
Kumar, Prashant; Cabaj, Malgorzata Katarzyna; Pazio, Aleksandra; Dominiak, Paulina Maria; IUCrJ 5 (2018) –; doi:10.1107/S2052252518006346

data_1549527
_publ_section_title
;
 Protonated nucleobases are not fully ionized in their chloride salt
 crystals and form metastable base pairs further stabilized by the
 surrounding anions
;
_journal_issue                   4
_journal_name_full               IUCrJ
_journal_page_first
;
;
_journal_paper_doi               10.1107/S2052252518006346
_journal_volume                  5
_journal_year                    2018
_chemical_formula_moiety         '0.5(C5 H7 N5 O), Cl'
_chemical_formula_sum            'C2.5 H3.5 Cl N2.5 O0.5'
_chemical_formula_weight         112.25
_chemical_name_systematic        'guaninium dichloride'
_space_group_crystal_system      orthorhombic
_space_group_IT_number           62
_space_group_name_Hall           '-P 2ac 2n'
_space_group_name_H-M_alt        'P n m a'
_symmetry_Int_Tables_number      62
_symmetry_space_group_name_Hall  '-P 2ac 2n'
_symmetry_space_group_name_H-M   'P n m a'
_atom_sites_solution_hydrogens   difmap
_atom_sites_solution_primary     direct
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_cell_angle_alpha                90
_cell_angle_beta                 90
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_cell_length_b                   6.4841(2)
_cell_length_c                   9.8600(4)
_cell_measurement_reflns_used    1075
_cell_measurement_temperature    100
_cell_measurement_theta_max      41.1062
_cell_measurement_theta_min      2.5815
_cell_volume                     869.10(5)
_computing_cell_refinement       'APEX2 v2013.10-0 (Bruker AXS)'
_computing_data_collection       'APEX2 v2013.10-0 (Bruker AXS)'
_computing_data_reduction        'SAINT V8.34A (Bruker AXS Inc., 2013)'
_computing_structure_refinement  'MoPro (J. Appl. Cryst. 2005, 38, 38-54)'
_computing_structure_solution    'ShelXS (Sheldrick, 2008)'
_diffrn_ambient_environment      N~2~
_diffrn_ambient_temperature      100
_diffrn_detector                 'CCD plate'
_diffrn_detector_type            'APEX II'
_diffrn_measured_fraction_theta_full 0.995
_diffrn_measured_fraction_theta_max 0.995
_diffrn_measurement_details
;
  1 phi   -350.17    9.33   0.5000   59.9780
omega____ theta____ kappa____ phi______ frames
 -49.0876  -72.2100  -30.1706     -     719

  2 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017  -67.0280 237

  3 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017  112.9717 237

  4 phi     -9.83  349.67   0.5000   59.9970
omega____ theta____ kappa____ phi______ frames
  12.8045  -72.2100   30.1706     -     719

  5 phi   -332.86   26.64   0.5000   60.0120
omega____ theta____ kappa____ phi______ frames
 -39.4784  -72.2100  -77.1464     -     719

  6 omega  -30.41   84.09   0.5000   20.0000
omega____ theta____ kappa____ phi______ frames
    -        0.0790   73.7598 -115.7463 229

  7 omega    7.79   77.29   0.5000   20.0000
omega____ theta____ kappa____ phi______ frames
    -       27.6250 -114.9409  133.0056 139

  8 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017 -139.0288 237

  9 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017   40.9717 237

 10 omega  232.79  348.79   0.5000   40.0000
omega____ theta____ kappa____ phi______ frames
    -      -42.2100  -73.7597 -154.2539 232

 11 omega  232.79  348.79   0.5000   40.0000
omega____ theta____ kappa____ phi______ frames
    -      -42.2100  -73.7597  -64.2541 232

 12 omega  232.79  348.79   0.5000   40.0000
omega____ theta____ kappa____ phi______ frames
    -      -42.2100  -73.7597   25.7466 232

 13 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017  -31.0291 237

 14 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017  148.9717 237

 15 omega  232.79  348.79   0.5000   40.0000
omega____ theta____ kappa____ phi______ frames
    -      -42.2100  -73.7597  115.7467 232

 16 omega   25.76   56.76   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       59.0570   79.0325   -2.1000 62

 17 omega -107.31   11.69   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2020 -103.0280 238

 18 omega -107.31   11.69   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2020 -175.0280 238

 19 phi   -332.86   26.64   0.5000   49.9840
omega____ theta____ kappa____ phi______ frames
 -24.4784  -57.2100  -77.1464     -     719

 20 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017    4.9720 237

 21 omega -107.31   11.19   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100   86.2017   76.9709 237

 22 omega  -97.21   19.29   0.5000   20.0000
omega____ theta____ kappa____ phi______ frames
    -      -12.2100  -73.7597   25.7466 233

 23 omega   29.49  145.99   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       61.5359   75.4491  106.8141 233

 24 omega   24.17  141.17   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       56.2399   75.5917 -152.3958 234

 25 omega   25.21  141.71   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       57.2949   75.6778   30.3042 233

 26 omega   30.41  147.91   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       63.0230   77.2097  -78.1884 235

 27 omega   29.13  146.63   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       61.8420   77.7603  -39.4431 235

 28 omega   27.46  143.96   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       59.0420   74.2152   87.9108 233

 29 omega   28.66  144.16   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       59.3800   72.1659 -111.6073 231

 30 omega   26.23  142.23   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       57.9040   74.7616   67.1753 232

 31 phi   -332.86   26.64   0.5000   39.9980
omega____ theta____ kappa____ phi______ frames
  -9.4784  -42.2100  -77.1464     -     719

 32 omega  -30.41   84.09   0.5000   20.0000
omega____ theta____ kappa____ phi______ frames
    -        0.0790   73.7598   64.2537 229

 33 omega   28.53  142.03   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       57.7459   67.5805  179.8736 227

 34 omega   28.05  143.05   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       58.0690   69.4456  146.4266 230

 35 omega   29.86  145.36   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       60.5080   71.7520 -133.3569 231

 36 omega   32.11  148.11   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       63.2809   73.3342   42.6552 232

 37 omega   29.10  145.10   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       60.2780   73.3933  104.5231 232

 38 omega   24.27  141.27   0.5000   50.0000
omega____ theta____ kappa____ phi______ frames
    -       56.4359   76.1275   11.3628 234

 39 omega  203.79  318.29   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100  -73.7597   61.7459 229

 40 omega  203.79  318.29   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100  -73.7597  -46.2541 229

 41 omega  203.79  318.29   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100  -73.7597  133.7467 229

 42 omega  203.79  318.29   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100  -73.7597  -10.2539 229

 43 omega  203.79  318.29   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100  -73.7597   25.7466 229

 44 omega  203.79  317.79   0.5000   59.9980
omega____ theta____ kappa____ phi______ frames
    -      -72.2100  -73.7597  169.7461 228
;
_diffrn_measurement_device       'four-circle diffractometer'
_diffrn_measurement_device_type  'Bruker APEX II ULTRA'
_diffrn_measurement_method       '\f and \w scans'
_diffrn_orient_matrix_UB_11      -0.0394875000
_diffrn_orient_matrix_UB_12      -0.0463023000
_diffrn_orient_matrix_UB_13      -0.0121293000
_diffrn_orient_matrix_UB_21      -0.0041713000
_diffrn_orient_matrix_UB_22      0.0185261000
_diffrn_orient_matrix_UB_23      -0.1052764000
_diffrn_orient_matrix_UB_31      0.0337945000
_diffrn_orient_matrix_UB_32      -0.0519156000
_diffrn_orient_matrix_UB_33      -0.0270700000
_diffrn_radiation_monochromator  mirror
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_diffrn_radiation_source         'Enhance (Mo) X-ray Source'
_diffrn_radiation_type           'Mo K\a'
_diffrn_radiation_wavelength     0.71073
_diffrn_reflns_av_R_equivalents  0.0586
_diffrn_reflns_av_sigmaI/netI    0.0495
_diffrn_reflns_limit_h_max       14
_diffrn_reflns_limit_h_min       -14
_diffrn_reflns_limit_k_max       22
_diffrn_reflns_limit_k_min       -22
_diffrn_reflns_limit_l_max       30
_diffrn_reflns_limit_l_min       -30
_diffrn_reflns_number            232874
_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        53.95
_diffrn_reflns_theta_max         53.95
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_exptl_absorpt_coefficient_mu    0.716
_exptl_absorpt_correction_T_max  0.907
_exptl_absorpt_correction_T_min  0.863
_exptl_absorpt_correction_type   multi-scan
_exptl_absorpt_process_details
;
 R.H. Blessing, Acta Cryst. (1995), A51, 33-38
;
_exptl_crystal_colour            'opaque colorless'
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_refine_ls_R_factor_gt           0.0179
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_refine_ls_shift/su_mean         0.000
_refine_ls_structure_factor_coef F
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_reflns_d_resolution_high        0.440
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