# Supplementary Material (ESI) for ChemComm # This journal is (c) The Royal Society of Chemistry 2001 # CCDC Number: 182/1850 data_pv4 _audit_creation_method SHELXL-97 _chemical_name_systematic ; '2,3,5,6-Pyrazine tetracarboxylic acid dihydrate'; _chemical_name_common '2,3,5,6-Pyrazine tetracarboxylic acid dihydrate'_chemical_formula_sum 'C8 H8 N2 O10' _chemical_formula_weight 292.16 _chemical_melting_point 475 loop_ _atom_type_symbol _atom_type_description _atom_type_scat_dispersion_real _atom_type_scat_dispersion_imag _atom_type_scat_source 'C' 'C' 0.0033 0.0016 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' 'H' 'H' 0.0000 0.0000 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' 'N' 'N' 0.0061 0.0033 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' 'O' 'O' 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' _symmetry_cell_setting triclinic _symmetry_space_group_name_H-M 'P -1' loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x, -y, -z' _cell_length_a 5.4409(3) _cell_length_b 6.4041(3) _cell_length_c 8.6995(3) _cell_angle_alpha 98.572(3) _cell_angle_beta 107.374(3) _cell_angle_gamma 105.519(3) _cell_volume 269.97(2) _cell_formula_units_Z 1_cell_measurement_temperature 123(2) _cell_measurement_reflns_used 1219 _cell_measurement_theta_min 3.41 _cell_measurement_theta_max 27.44 _exptl_crystal_description needle _exptl_crystal_colour colorless_exptl_crystal_density_meas 'not measured' _exptl_crystal_density_diffrn 1.797 _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 150 _exptl_absorpt_coefficient_mu 0.171 _exptl_absorpt_correction_type none _exptl_special_details ; ? ; _diffrn_ambient_temperature 123(2) _diffrn_radiation_wavelength 0.71073 _diffrn_radiation_type MoK\a _diffrn_radiation_source 'normal focus for X-ray tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device 'Nonius Kappa CCD' _diffrn_measurement_method '\w scans'_diffrn_standards_decay_% 'less than 1'_diffrn_reflns_number 2300 _diffrn_reflns_av_R_equivalents 0.0121 _diffrn_reflns_av_sigmaI/netI 0.0253 _diffrn_reflns_limit_h_min -7 _diffrn_reflns_limit_h_max 7 _diffrn_reflns_limit_k_min -8 _diffrn_reflns_limit_k_max 8 _diffrn_reflns_limit_l_min -11 _diffrn_reflns_limit_l_max 11 _diffrn_reflns_theta_min 3.41 _diffrn_reflns_theta_max 27.44 _reflns_number_total 1219 _reflns_number_observed 1125 _reflns_observed_criterion >2sigma(I) _computing_data_collection '"Collect" data collection software, Nonius 1998. '_computing_cell_refinement DENZO-SMN _computing_data_reduction SCALEPACK _computing_structure_solution 'SHELXS-97 (Sheldrick, 1997)' _computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)' _computing_molecular_graphics 'ORTEP and PLUTON ' _computing_publication_material SHELXL-97 _refine_special_details ; Refinement on F^2^ for ALL reflections except for 17 with very negative F^2^ or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The observed criterion of F^2^ > 2sigma(F^2^) is used only for calculating _R_factor_obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. ; _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_weighting_scheme 'calc w=1/[\s^2^(Fo^2^)+(0.0411P)^2^+0.1017P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _atom_sites_solution_hydrogens geom _refine_ls_hydrogen_treatment refall _refine_ls_extinction_method none _refine_ls_number_reflns 1202 _refine_ls_number_parameters 107 _refine_ls_number_restraints 0 _refine_ls_R_factor_all 0.0327 _refine_ls_R_factor_obs 0.0302 _refine_ls_wR_factor_all 0.0823 _refine_ls_wR_factor_obs 0.0803 _refine_ls_goodness_of_fit_all 1.061 _refine_ls_goodness_of_fit_obs 1.082 _refine_ls_restrained_S_all 1.061 _refine_ls_restrained_S_obs 1.082 _refine_ls_shift/esd_max 0.000 _refine_ls_shift/esd_mean 0.000 loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_thermal_displace_type _atom_site_occupancy _atom_site_calc_flag _atom_site_refinement_flags _atom_site_disorder_group O2 O 0.2537(2) 0.94900(13) 0.09048(10) 0.0163(2) Uani 1 d . . H2 H 0.2360(44) 1.0775(39) 0.1506(26) 0.053(6) Uiso 1 d . . O3 O 0.6351(2) 1.00251(14) 0.30665(10) 0.0193(2) Uani 1 d . . O4 O 0.7472(2) 0.6144(2) 0.44454(10) 0.0242(2) Uani 1 d . . O5 O 1.0968(2) 0.7796(2) 0.36953(10) 0.0212(2) Uani 1 d . . H5 H 1.1841(39) 0.8257(32) 0.4822(24) 0.039(5) Uiso 1 d . . N6 N 0.3101(2) 0.5957(2) -0.07642(11) 0.0123(2) Uani 1 d . . C7 C 0.4610(2) 0.8972(2) 0.17216(13) 0.0129(2) Uani 1 d . . C8 C 0.4784(2) 0.6852(2) 0.08150(13) 0.0117(2) Uani 1 d . . C9 C 0.6683(2) 0.5881(2) 0.15839(13) 0.0121(2) Uani 1 d . . C10 C 0.8416(2) 0.6668(2) 0.34187(13) 0.0136(2) Uani 1 d . . H1A H 0.2219(39) 0.3267(32) 0.3289(25) 0.042(5) Uiso 1 d . . H1B H 0.0203(45) 0.2839(33) 0.1737(26) 0.044(5) Uiso 1 d . . O1 O 0.1840(2) 0.29009(14) 0.21977(10) 0.0158(2) Uani 1 d . . loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_23 _atom_site_aniso_U_13 _atom_site_aniso_U_12 O2 0.0178(4) 0.0164(4) 0.0127(4) 0.0000(3) 0.0014(3) 0.0092(3) O3 0.0180(4) 0.0195(4) 0.0133(4) -0.0038(3) -0.0011(3) 0.0069(3) O4 0.0221(5) 0.0317(5) 0.0115(4) 0.0038(4) 0.0041(3) 0.0008(4) O5 0.0141(4) 0.0300(5) 0.0110(4) -0.0002(3) 0.0007(3) 0.0008(3) N6 0.0126(4) 0.0132(4) 0.0097(4) 0.0020(4) 0.0029(4) 0.0037(3) C7 0.0137(5) 0.0137(5) 0.0109(5) 0.0028(4) 0.0043(4) 0.0043(4) C8 0.0118(5) 0.0119(5) 0.0092(5) 0.0016(4) 0.0025(4) 0.0027(4) C9 0.0120(5) 0.0130(5) 0.0095(5) 0.0019(4) 0.0030(4) 0.0027(4) C10 0.0151(5) 0.0127(5) 0.0115(5) 0.0011(4) 0.0022(4) 0.0062(4) O1 0.0153(4) 0.0187(4) 0.0115(4) 0.0001(3) 0.0019(3) 0.0080(3) _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag O2 C7 1.2953(13) . ? O2 H2 0.95(2) . ? O3 C7 1.2174(14) . ? O4 C10 1.2021(14) . ? O5 C10 1.3115(14) . ? O5 H5 0.91(2) . ? N6 C9 1.3347(14) 2_665 ? N6 C8 1.3371(14) . ? C7 C8 1.5063(15) . ? C8 C9 1.3991(15) . ? C9 N6 1.3347(14) 2_665 ? C9 C10 1.5159(14) . ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag C7 O2 H2 113.1(13) . . ? C10 O5 H5 107.0(12) . . ? C9 N6 C8 117.64(9) 2_665 . ? O3 C7 O2 126.97(10) . . ? O3 C7 C8 119.94(10) . . ? O2 C7 C8 113.08(9) . . ? N6 C8 C9 121.09(10) . . ? N6 C8 C7 117.66(9) . . ? C9 C8 C7 121.24(9) . . ? N6 C9 C8 121.27(10) 2_665 . ? N6 C9 C10 115.18(9) 2_665 . ? C8 C9 C10 123.27(10) . . ? O4 C10 O5 126.34(10) . . ? O4 C10 C9 120.77(10) . . ? O5 C10 C9 112.74(9) . . ? H1A O1 H1B 106.9(18) . . ? _refine_diff_density_max 0.330 _refine_diff_density_min -0.218 _refine_diff_density_rms 0.047 data_pv1a _audit_creation_method SHELXL-97 _chemical_name_systematic ; '5,6-Dimethyl pyrazine-2,3-dicarboxylic acid dihydrate' ; _chemical_name_common '5,6-Dimethyl pyrazine-2,3-dicarboxylic acid dihydrate'_chemical_formula_sum 'C8 H12 N2 O6'_chemical_formula_weight 232.19 _chemical_melting_point 478 loop_ _atom_type_symbol _atom_type_description _atom_type_scat_dispersion_real _atom_type_scat_dispersion_imag _atom_type_scat_source 'C' 'C' 0.0033 0.0016 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' 'H' 'H' 0.0000 0.0000 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' 'N' 'N' 0.0061 0.0033 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' 'O' 'O' 0.0106 0.0060 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' _symmetry_cell_setting orthorhombic_symmetry_space_group_name_H-M Pbcn loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x+1/2, -y+1/2, z+1/2' '-x, y, -z+1/2' 'x+1/2, -y+1/2, -z' '-x, -y, -z' 'x-1/2, y-1/2, -z-1/2' 'x, -y, z-1/2' '-x-1/2, y-1/2, z' _cell_length_a 12.6454(3) _cell_length_b 9.0812(3) _cell_length_c 8.8800(3) _cell_angle_alpha 90.00 _cell_angle_beta 90.00 _cell_angle_gamma 90.00 _cell_volume 1019.74(5) _cell_formula_units_Z 4 _cell_measurement_temperature 123(2) _cell_measurement_reflns_used 1161 _cell_measurement_theta_min 3.59 _cell_measurement_theta_max 27.48 _exptl_crystal_description cubic_exptl_crystal_colour 'pale yellow' _exptl_crystal_density_meas 'not measured'_exptl_crystal_density_diffrn 1.512 _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 488 _exptl_absorpt_coefficient_mu 0.131 _exptl_absorpt_correction_type none _exptl_special_details ; ? ; _diffrn_ambient_temperature 123(2) _diffrn_radiation_wavelength 0.71073 _diffrn_radiation_type MoK\a _diffrn_radiation_source 'normal focus for X-ray tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device_type 'Nonius Kappa CCD' _diffrn_measurement_method '\w scans' _diffrn_standards_decay_% 'less than 1' _diffrn_reflns_number 2132 _diffrn_reflns_av_R_equivalents 0.0112 _diffrn_reflns_av_sigmaI/netI 0.0212 _diffrn_reflns_limit_h_min -16 _diffrn_reflns_limit_h_max 16 _diffrn_reflns_limit_k_min -11 _diffrn_reflns_limit_k_max 11 _diffrn_reflns_limit_l_min -11 _diffrn_reflns_limit_l_max 11 _diffrn_reflns_theta_min 3.59 _diffrn_reflns_theta_max 27.48 _reflns_number_total 1161 _reflns_number_gt 1059 _reflns_threshold_expression '>2sigma(I)' _computing_data_collection '"Collect" data collection software, Nonius 1998. ' _computing_cell_refinement DENZO-SMN _computing_data_reduction SCALEPACK_computing_structure_solution 'SHELXS-97 (Sheldrick, 1990)' _computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)' _computing_molecular_graphics 'ORTEP and PLUTON' _computing_publication_material SHELXL-97 _refine_special_details ; Refinement of F^2^ against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F^2^, conventional R-factors R are based on F, with F set to zero for negative F^2^. The threshold expression of F^2^ > 2sigma(F^2^) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F^2^ are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. ; _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_weighting_scheme calc _refine_ls_weighting_details 'calc w=1/[\s^2^(Fo^2^)+(0.0455P)^2^+0.3365P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _atom_sites_solution_hydrogens geom _refine_ls_hydrogen_treatment refall _refine_ls_extinction_method none _refine_ls_number_reflns 1161 _refine_ls_number_parameters 97 _refine_ls_number_restraints 0 _refine_ls_R_factor_all 0.0344 _refine_ls_R_factor_gt 0.0313 _refine_ls_wR_factor_ref 0.0868 _refine_ls_wR_factor_gt 0.0845 _refine_ls_goodness_of_fit_ref 1.069 _refine_ls_restrained_S_all 1.069 _refine_ls_shift/su_max 0.000 _refine_ls_shift/su_mean 0.000 loop_ _atom_site_label _atom_site_type_symbol _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_occupancy _atom_site_symmetry_multiplicit _atom_site_calc_flag _atom_site_refinement_flags _atom_site_disorder_assembly _atom_site_disorder_group O1 O 0.38118(7) 0.84800(9) 0.24760(9) 0.0280(2) Uani 1 1 d . . . O3 O 0.25029(7) 0.45791(9) 0.57338(10) 0.0237(2) Uani 1 1 d . . . N5 N 0.41552(7) 0.48572(10) 0.34931(10) 0.0172(2) Uani 1 1 d . . . O2 O 0.36048(6) 0.74656(9) 0.47656(9) 0.0221(2) Uani 1 1 d . . . C6 C 0.45767(8) 0.35904(11) 0.30252(12) 0.0172(2) Uani 1 1 d . . . C7 C 0.41012(9) 0.21990(12) 0.36205(13) 0.0221(3) Uani 1 1 d . . . C3 C 0.39632(8) 0.74994(11) 0.33768(12) 0.0180(2) Uani 1 1 d . . . C4 C 0.45635(8) 0.61243(11) 0.29719(11) 0.0168(2) Uani 1 1 d . . . H7C H 0.3808(13) 0.2338(18) 0.464(2) 0.037(4) Uiso 1 1 d . . . H7B H 0.4602(15) 0.1399(19) 0.367(2) 0.045(5) Uiso 1 1 d . . . H2 H 0.3217(15) 0.835(2) 0.502(2) 0.050(5) Uiso 1 1 d . . . H7A H 0.3528(16) 0.190(2) 0.296(2) 0.050(5) Uiso 1 1 d . . . H3B H 0.2979(19) 0.493(2) 0.513(3) 0.053(5) Uiso 1 1 d . . . H3A H 0.2202(15) 0.530(2) 0.622(2) 0.052(5) Uiso 1 1 d . . . loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_23 _atom_site_aniso_U_13 _atom_site_aniso_U_12 O1 0.0394(5) 0.0208(4) 0.0237(4) 0.0035(3) 0.0012(3) 0.0085(3) O3 0.0241(4) 0.0212(4) 0.0258(4) -0.0031(3) 0.0029(3) -0.0039(3) N5 0.0183(4) 0.0172(4) 0.0160(4) 0.0004(3) -0.0020(3) -0.0004(3) O2 0.0252(4) 0.0207(4) 0.0203(4) -0.0003(3) 0.0038(3) 0.0055(3) C6 0.0188(5) 0.0167(5) 0.0160(5) 0.0001(4) -0.0036(4) -0.0002(4) C7 0.0259(6) 0.0177(5) 0.0227(6) 0.0006(4) 0.0021(5) -0.0031(4) C3 0.0174(5) 0.0172(5) 0.0193(5) -0.0014(4) -0.0018(4) -0.0004(4) C4 0.0184(5) 0.0165(5) 0.0157(5) 0.0000(4) -0.0026(4) 0.0002(4) _geom_special_details ; All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_distance _geom_bond_site_symmetry_2 _geom_bond_publ_flag O1 C3 1.2122(13) . ? N5 C6 1.3343(13) . ? N5 C4 1.3435(14) . ? O2 C3 1.3142(14) . ? C6 C6 1.420(2) 3_655 ? C6 C7 1.4959(14) . ? C3 C4 1.5050(14) . ? C4 C4 1.386(2) 3_655 ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle_publ_flag C6 N5 C4 118.53(9) . . ? N5 C6 C6 120.39(6) . 3_655 ? N5 C6 C7 117.23(10) . . ? C6 C6 C7 122.36(6) 3_655 . ? O1 C3 O2 125.59(10) . . ? O1 C3 C4 122.11(10) . . ? O2 C3 C4 112.26(9) . . ? N5 C4 C4 120.96(6) . 3_655 ? N5 C4 C3 115.75(9) . . ? C4 C4 C3 123.11(6) 3_655 . ? _diffrn_measured_fraction_theta_max 0.991 _diffrn_reflns_theta_full 27.48 _diffrn_measured_fraction_theta_full 0.991 _refine_diff_density_max 0.251 _refine_diff_density_min -0.216 _refine_diff_density_rms 0.042