############################################################################## # # # This CIF contains the data in a paper accepted for publication in # # Acta Crystallographica Section E. It conforms to the requirements of # # Notes for Authors for Acta Crystallographica Section E, and has been # # peer reviewed under the auspices of the IUCr Commission on Journals. # # # # Full details of the Crystallographic Information File format # # are given in the paper "The Crystallographic Information File (CIF): # # a New Standard Archive File for Crystallography" by S. R. Hall, F. H. # # Allen and I. D. Brown [Acta Cryst. (1991), A47, 655-685]. # # # # The current version of the core CIF dictionary is obtainable from # # ftp://ftp.iucr.org/pub/cif_core.dic. # # # # Software is freely available for graphical display of the structure(s) # # in this CIF. For information consult the CIF software page # # http://www.iucr.org/resources/cif/software. # # # # This file may be used for bona fide research purposes within the # # scientific community so long as proper attribution is given to the journal # # article from which it was obtained. # # # ############################################################################## data_I _audit_creation_method SHELXL-97 _chemical_name_systematic ; (E,E)-N^1^,N^4^-Bis(2,6- difluorobenzylidene)butane-1,4-diamine ; _chemical_name_common ; ; _chemical_formula_moiety 'C18 H16 F4 N2' _chemical_formula_sum 'C18 H16 F4 N2' _chemical_formula_iupac 'C18 H16 F4 N2' _chemical_formula_weight 336.33 _chemical_melting_point ? _symmetry_cell_setting triclinic _symmetry_space_group_name_H-M 'P -1' _symmetry_space_group_name_Hall '-P 1' loop_ _symmetry_equiv_pos_as_xyz 'x, y, z' '-x, -y, -z' _cell_length_a 6.4672(8) _cell_length_b 8.9296(12) _cell_length_c 14.4939(19) _cell_angle_alpha 104.956(2) _cell_angle_beta 94.474(2) _cell_angle_gamma 93.679(2) _cell_volume 803.10(18) _cell_formula_units_Z 2 _cell_measurement_reflns_used 4637 _cell_measurement_theta_min 2.88 _cell_measurement_theta_max 28.27 _cell_measurement_temperature 150(2) _exptl_crystal_description block _exptl_crystal_colour colourless _exptl_crystal_size_max 0.34 _exptl_crystal_size_mid 0.30 _exptl_crystal_size_min 0.20 _exptl_crystal_density_diffrn 1.391 _exptl_crystal_density_meas ? _exptl_crystal_density_method 'not measured' _exptl_crystal_F_000 348 _exptl_absorpt_coefficient_mu 0.115 _exptl_absorpt_correction_type multi-scan _exptl_absorpt_process_details '(SADABS; Bruker, 2005)' _exptl_absorpt_correction_T_min 0.962 _exptl_absorpt_correction_T_max 0.977 _exptl_special_details ; The low-temperature data were collected with the Oxford Cyrosystems Cryostream low-temperature attachment. ; _diffrn_ambient_temperature 150(2) _diffrn_radiation_type MoK\a _diffrn_radiation_wavelength 0.71073 _diffrn_radiation_source 'fine-focus sealed tube' _diffrn_radiation_monochromator graphite _diffrn_measurement_device_type ; Bruker SMART 1K CCD area-detector ; _diffrn_measurement_method '\w scans' _diffrn_detector_area_resol_mean 8.33 _diffrn_reflns_number 5828 _diffrn_reflns_av_R_equivalents 0.0191 _diffrn_reflns_av_sigmaI/netI 0.0251 _diffrn_reflns_theta_min 2.37 _diffrn_reflns_theta_max 25.00 _diffrn_reflns_theta_full 25.00 _diffrn_measured_fraction_theta_max 0.992 _diffrn_measured_fraction_theta_full 0.992 _diffrn_reflns_limit_h_min -7 _diffrn_reflns_limit_h_max 7 _diffrn_reflns_limit_k_min -10 _diffrn_reflns_limit_k_max 10 _diffrn_reflns_limit_l_min -16 _diffrn_reflns_limit_l_max 17 _diffrn_standards_number 0 _diffrn_standards_interval_count . _diffrn_standards_interval_time . _diffrn_standards_decay_% . _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^ > \s(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. ; _reflns_number_total 2819 _reflns_number_gt 2394 _reflns_threshold_expression 'I>2\s(I)' _refine_ls_structure_factor_coef Fsqd _refine_ls_matrix_type full _refine_ls_R_factor_all 0.0454 _refine_ls_R_factor_gt 0.0369 _refine_ls_wR_factor_gt 0.0931 _refine_ls_wR_factor_ref 0.0998 _refine_ls_goodness_of_fit_ref 1.110 _refine_ls_restrained_S_all 1.110 _refine_ls_number_reflns 2819 _refine_ls_number_parameters 218 _refine_ls_number_restraints 0 _refine_ls_hydrogen_treatment constr _refine_ls_weighting_scheme calc _refine_ls_weighting_details 'calc w=1/[\s^2^(Fo^2^)+(0.0437P)^2^+0.2616P] where P=(Fo^2^+2Fc^2^)/3' _atom_sites_solution_hydrogens geom _atom_sites_solution_primary direct _atom_sites_solution_secondary difmap _refine_ls_shift/su_max 0.000 _refine_ls_shift/su_mean 0.000 _refine_diff_density_max 0.248 _refine_diff_density_min -0.174 _refine_ls_extinction_method 'SHELXL97 (Sheldrick, 2008)' _refine_ls_extinction_coef 0.0064(19) _refine_ls_extinction_expression 'Fc^*^=kFc[1+0.001xFc^2^\l^3^/sin(2\q)]^-1/4^' 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' 'F' 'F' 0.0171 0.0103 'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4' _computing_data_collection 'SMART (Bruker, 2005)' _computing_cell_refinement 'SAINT (Bruker, 2005)' _computing_data_reduction 'SAINT (Bruker, 2005)' _computing_structure_solution 'SHELXS97 (Sheldrick, 2008)' _computing_structure_refinement 'SHELXL97 (Sheldrick, 2008)' _computing_molecular_graphics 'SHELXTL (Sheldrick, 2008)' _computing_publication_material 'SHELXTL (Sheldrick, 2008) and PLATON (Spek,2009)' loop_ _atom_site_type_symbol _atom_site_label _atom_site_fract_x _atom_site_fract_y _atom_site_fract_z _atom_site_U_iso_or_equiv _atom_site_adp_type _atom_site_calc_flag _atom_site_refinement_flags _atom_site_occupancy _atom_site_symmetry_multiplicity _atom_site_disorder_assembly _atom_site_disorder_group N N1 0.1808(2) 0.73556(16) 0.64201(10) 0.0304(3) Uani d . 1 1 . . N N2 0.1964(2) 0.08666(15) 0.86448(9) 0.0280(3) Uani d . 1 1 . . F F1 0.19530(16) 1.11574(12) 0.54522(8) 0.0423(3) Uani d . 1 1 . . F F2 0.57474(16) 0.85519(11) 0.73666(7) 0.0392(3) Uani d . 1 1 . . F F3 0.14208(16) 0.33304(13) 0.78309(9) 0.0486(3) Uani d . 1 1 . . F F4 0.76402(16) 0.30222(12) 0.96638(8) 0.0424(3) Uani d . 1 1 . . C C1 0.3727(2) 1.10083(19) 0.59734(11) 0.0274(4) Uani d . 1 1 . . C C2 0.5378(3) 1.21002(19) 0.60645(12) 0.0327(4) Uani d . 1 1 . . H H2 0.5284 1.2924 0.5764 0.039 Uiso calc R 1 1 . . C C3 0.7184(3) 1.1967(2) 0.66064(12) 0.0323(4) Uani d . 1 1 . . H H3 0.8348 1.2707 0.6677 0.039 Uiso calc R 1 1 . . C C4 0.7309(2) 1.07689(19) 0.70447(12) 0.0290(4) Uani d . 1 1 . . H H4 0.8539 1.0686 0.7425 0.035 Uiso calc R 1 1 . . C C5 0.5610(2) 0.96960(18) 0.69179(11) 0.0260(4) Uani d . 1 1 . . C C6 0.3742(2) 0.97517(17) 0.63782(10) 0.0236(3) Uani d . 1 1 . . C C7 0.1858(2) 0.86668(18) 0.62385(11) 0.0262(4) Uani d . 1 1 . . H H7 0.0593 0.8975 0.5995 0.031 Uiso calc R 1 1 . . C C8 -0.0223(3) 0.6452(2) 0.62406(12) 0.0353(4) Uani d . 1 1 . . H H8A -0.1286 0.7057 0.6011 0.042 Uiso calc R 1 1 . . H H8B -0.0627 0.6257 0.6847 0.042 Uiso calc R 1 1 . . C C9 -0.0163(3) 0.49050(19) 0.54960(12) 0.0324(4) Uani d . 1 1 . . H H9A 0.0978 0.4343 0.5706 0.039 Uiso calc R 1 1 . . H H9B -0.1488 0.4263 0.5459 0.039 Uiso calc R 1 1 . . C C10 0.3370(2) 0.38982(19) 0.82192(12) 0.0285(4) Uani d . 1 1 . . C C11 0.4160(3) 0.52544(19) 0.80426(12) 0.0335(4) Uani d . 1 1 . . H H11 0.3351 0.5768 0.7664 0.040 Uiso calc R 1 1 . . C C12 0.6160(3) 0.58532(19) 0.84294(12) 0.0336(4) Uani d . 1 1 . . H H12 0.6728 0.6790 0.8316 0.040 Uiso calc R 1 1 . . C C13 0.7339(3) 0.51022(19) 0.89783(12) 0.0331(4) Uani d . 1 1 . . H H13 0.8712 0.5509 0.9245 0.040 Uiso calc R 1 1 . . C C14 0.6470(3) 0.37536(18) 0.91265(12) 0.0275(4) Uani d . 1 1 . . C C15 0.4472(2) 0.30737(17) 0.87626(11) 0.0245(3) Uani d . 1 1 . . C C16 0.3732(2) 0.15886(18) 0.89413(11) 0.0261(4) Uani d . 1 1 . . H H16 0.4662 0.1137 0.9310 0.031 Uiso calc R 1 1 . . C C17 0.1558(3) -0.06100(18) 0.88829(12) 0.0298(4) Uani d . 1 1 . . H H17A 0.2825 -0.0846 0.9229 0.036 Uiso calc R 1 1 . . H H17B 0.1225 -0.1454 0.8284 0.036 Uiso calc R 1 1 . . C C18 -0.0243(2) -0.05570(17) 0.95036(11) 0.0248(3) Uani d . 1 1 . . H H18A -0.1474 -0.0238 0.9176 0.030 Uiso calc R 1 1 . . H H18B -0.0605 -0.1615 0.9571 0.030 Uiso calc R 1 1 . . loop_ _atom_site_aniso_label _atom_site_aniso_U_11 _atom_site_aniso_U_22 _atom_site_aniso_U_33 _atom_site_aniso_U_12 _atom_site_aniso_U_13 _atom_site_aniso_U_23 N1 0.0337(8) 0.0262(7) 0.0285(7) -0.0040(6) 0.0007(6) 0.0044(6) N2 0.0307(8) 0.0286(7) 0.0266(7) -0.0016(6) 0.0052(6) 0.0109(6) F1 0.0344(6) 0.0431(6) 0.0530(7) -0.0030(5) -0.0134(5) 0.0260(5) F2 0.0374(6) 0.0374(6) 0.0489(6) 0.0016(4) -0.0052(5) 0.0257(5) F3 0.0304(6) 0.0456(6) 0.0743(8) -0.0077(5) -0.0171(5) 0.0333(6) F4 0.0352(6) 0.0387(6) 0.0568(7) -0.0022(4) -0.0143(5) 0.0255(5) C1 0.0260(8) 0.0301(8) 0.0258(8) 0.0033(7) -0.0027(6) 0.0084(7) C2 0.0371(10) 0.0287(9) 0.0350(9) -0.0022(7) 0.0009(7) 0.0155(7) C3 0.0289(9) 0.0348(9) 0.0318(9) -0.0058(7) 0.0035(7) 0.0081(7) C4 0.0230(8) 0.0350(9) 0.0283(8) 0.0023(7) 0.0009(7) 0.0075(7) C5 0.0308(9) 0.0254(8) 0.0241(8) 0.0054(7) 0.0048(7) 0.0092(6) C6 0.0265(8) 0.0231(8) 0.0200(7) 0.0018(6) 0.0043(6) 0.0029(6) C7 0.0260(8) 0.0274(8) 0.0242(8) 0.0016(6) 0.0019(6) 0.0053(6) C8 0.0376(10) 0.0330(9) 0.0333(9) -0.0093(8) 0.0081(8) 0.0069(7) C9 0.0382(10) 0.0260(8) 0.0323(9) -0.0096(7) 0.0027(7) 0.0098(7) C10 0.0240(8) 0.0277(8) 0.0334(9) 0.0004(7) -0.0009(7) 0.0088(7) C11 0.0392(10) 0.0287(9) 0.0349(9) 0.0038(7) -0.0034(8) 0.0142(7) C12 0.0421(10) 0.0228(8) 0.0365(9) -0.0041(7) 0.0004(8) 0.0116(7) C13 0.0301(9) 0.0285(9) 0.0382(10) -0.0053(7) -0.0045(7) 0.0087(7) C14 0.0278(9) 0.0261(8) 0.0297(8) 0.0048(7) -0.0007(7) 0.0100(7) C15 0.0262(8) 0.0229(8) 0.0250(8) 0.0031(6) 0.0055(6) 0.0062(6) C16 0.0271(9) 0.0269(8) 0.0269(8) 0.0058(7) 0.0049(7) 0.0101(7) C17 0.0370(9) 0.0243(8) 0.0284(9) -0.0009(7) 0.0064(7) 0.0076(7) C18 0.0281(8) 0.0212(7) 0.0246(8) -0.0053(6) -0.0003(6) 0.0080(6) _geom_special_details ; All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. ; loop_ _geom_bond_atom_site_label_1 _geom_bond_atom_site_label_2 _geom_bond_site_symmetry_2 _geom_bond_distance _geom_bond_publ_flag N1 C7 . 1.264(2) ? N1 C8 . 1.465(2) ? N2 C16 . 1.262(2) ? N2 C17 . 1.460(2) ? F1 C1 . 1.3568(18) ? F2 C5 . 1.3492(18) ? F3 C10 . 1.3504(19) ? F4 C14 . 1.3562(18) ? C1 C2 . 1.373(2) ? C1 C6 . 1.394(2) ? C2 C3 . 1.385(2) ? C2 H2 . 0.950 ? C3 C4 . 1.382(2) ? C3 H3 . 0.950 ? C4 C5 . 1.379(2) ? C4 H4 . 0.950 ? C5 C6 . 1.398(2) ? C6 C7 . 1.474(2) ? C7 H7 . 0.950 ? C8 C9 . 1.523(2) ? C8 H8A . 0.990 ? C8 H8B . 0.990 ? C9 C9 2_566 1.520(3) ? C9 H9A . 0.990 ? C9 H9B . 0.990 ? C10 C11 . 1.376(2) ? C10 C15 . 1.396(2) ? C11 C12 . 1.384(2) ? C11 H11 . 0.950 ? C12 C13 . 1.382(2) ? C12 H12 . 0.950 ? C13 C14 . 1.370(2) ? C13 H13 . 0.950 ? C14 C15 . 1.394(2) ? C15 C16 . 1.473(2) ? C16 H16 . 0.950 ? C17 C18 . 1.522(2) ? C17 H17A . 0.990 ? C17 H17B . 0.990 ? C18 C18 2_557 1.520(3) ? C18 H18A . 0.990 ? C18 H18B . 0.990 ? loop_ _geom_angle_atom_site_label_1 _geom_angle_atom_site_label_2 _geom_angle_atom_site_label_3 _geom_angle_site_symmetry_1 _geom_angle_site_symmetry_3 _geom_angle _geom_angle_publ_flag C7 N1 C8 . . 116.31(15) ? C16 N2 C17 . . 116.69(14) ? F1 C1 C2 . . 117.90(14) ? F1 C1 C6 . . 117.45(14) ? C2 C1 C6 . . 124.65(15) ? C1 C2 C3 . . 118.21(15) ? C1 C2 H2 . . 120.9 ? C3 C2 H2 . . 120.9 ? C4 C3 C2 . . 120.62(16) ? C4 C3 H3 . . 119.7 ? C2 C3 H3 . . 119.7 ? C5 C4 C3 . . 118.57(15) ? C5 C4 H4 . . 120.7 ? C3 C4 H4 . . 120.7 ? F2 C5 C4 . . 117.69(14) ? F2 C5 C6 . . 118.30(14) ? C4 C5 C6 . . 123.98(15) ? C1 C6 C5 . . 113.95(14) ? C1 C6 C7 . . 119.55(14) ? C5 C6 C7 . . 126.46(14) ? N1 C7 C6 . . 124.53(15) ? N1 C7 H7 . . 117.7 ? C6 C7 H7 . . 117.7 ? N1 C8 C9 . . 111.07(14) ? N1 C8 H8A . . 109.4 ? C9 C8 H8A . . 109.4 ? N1 C8 H8B . . 109.4 ? C9 C8 H8B . . 109.4 ? H8A C8 H8B . . 108.0 ? C9 C9 C8 2_566 . 112.91(17) ? C9 C9 H9A 2_566 . 109.0 ? C8 C9 H9A . . 109.0 ? C9 C9 H9B 2_566 . 109.0 ? C8 C9 H9B . . 109.0 ? H9A C9 H9B . . 107.8 ? F3 C10 C11 . . 117.55(14) ? F3 C10 C15 . . 118.52(14) ? C11 C10 C15 . . 123.92(15) ? C10 C11 C12 . . 118.54(15) ? C10 C11 H11 . . 120.7 ? C12 C11 H11 . . 120.7 ? C13 C12 C11 . . 120.70(15) ? C13 C12 H12 . . 119.7 ? C11 C12 H12 . . 119.7 ? C14 C13 C12 . . 118.07(16) ? C14 C13 H13 . . 121.0 ? C12 C13 H13 . . 121.0 ? F4 C14 C13 . . 117.68(15) ? F4 C14 C15 . . 117.52(14) ? C13 C14 C15 . . 124.80(15) ? C14 C15 C10 . . 113.96(14) ? C14 C15 C16 . . 119.93(14) ? C10 C15 C16 . . 126.07(15) ? N2 C16 C15 . . 125.39(15) ? N2 C16 H16 . . 117.3 ? C15 C16 H16 . . 117.3 ? N2 C17 C18 . . 111.32(13) ? N2 C17 H17A . . 109.4 ? C18 C17 H17A . . 109.4 ? N2 C17 H17B . . 109.4 ? C18 C17 H17B . . 109.4 ? H17A C17 H17B . . 108.0 ? C18 C18 C17 2_557 . 113.13(16) ? C18 C18 H18A 2_557 . 109.0 ? C17 C18 H18A . . 109.0 ? C18 C18 H18B 2_557 . 109.0 ? C17 C18 H18B . . 109.0 ? H18A C18 H18B . . 107.8 ? loop_ _geom_torsion_atom_site_label_1 _geom_torsion_atom_site_label_2 _geom_torsion_atom_site_label_3 _geom_torsion_atom_site_label_4 _geom_torsion_site_symmetry_1 _geom_torsion_site_symmetry_2 _geom_torsion_site_symmetry_3 _geom_torsion_site_symmetry_4 _geom_torsion _geom_torsion_publ_flag F1 C1 C2 C3 . . . . 179.14(15) ? C6 C1 C2 C3 . . . . -0.9(3) ? C1 C2 C3 C4 . . . . -0.2(3) ? C2 C3 C4 C5 . . . . 1.0(2) ? C3 C4 C5 F2 . . . . -178.75(14) ? C3 C4 C5 C6 . . . . -0.8(2) ? F1 C1 C6 C5 . . . . -178.90(13) ? C2 C1 C6 C5 . . . . 1.2(2) ? F1 C1 C6 C7 . . . . -0.8(2) ? C2 C1 C6 C7 . . . . 179.26(15) ? F2 C5 C6 C1 . . . . 177.68(13) ? C4 C5 C6 C1 . . . . -0.3(2) ? F2 C5 C6 C7 . . . . -0.2(2) ? C4 C5 C6 C7 . . . . -178.22(15) ? C8 N1 C7 C6 . . . . 179.47(14) ? C1 C6 C7 N1 . . . . 166.67(15) ? C5 C6 C7 N1 . . . . -15.5(2) ? C7 N1 C8 C9 . . . . 119.39(16) ? N1 C8 C9 C9 . . . 2_566 -66.7(2) ? F3 C10 C11 C12 . . . . -179.66(15) ? C15 C10 C11 C12 . . . . -0.5(3) ? C10 C11 C12 C13 . . . . 0.2(3) ? C11 C12 C13 C14 . . . . 0.0(3) ? C12 C13 C14 F4 . . . . 179.83(15) ? C12 C13 C14 C15 . . . . 0.1(3) ? F4 C14 C15 C10 . . . . 179.92(14) ? C13 C14 C15 C10 . . . . -0.3(2) ? F4 C14 C15 C16 . . . . -2.0(2) ? C13 C14 C15 C16 . . . . 177.79(16) ? F3 C10 C15 C14 . . . . 179.69(14) ? C11 C10 C15 C14 . . . . 0.5(2) ? F3 C10 C15 C16 . . . . 1.7(2) ? C11 C10 C15 C16 . . . . -177.44(16) ? C17 N2 C16 C15 . . . . 178.58(14) ? C14 C15 C16 N2 . . . . -179.69(15) ? C10 C15 C16 N2 . . . . -1.8(3) ? C16 N2 C17 C18 . . . . 118.07(16) ? N2 C17 C18 C18 . . . 2_557 -66.8(2) ? loop_ _geom_hbond_atom_site_label_D _geom_hbond_atom_site_label_H _geom_hbond_atom_site_label_A _geom_hbond_site_symmetry_A _geom_hbond_distance_DH _geom_hbond_distance_HA _geom_hbond_distance_DA _geom_hbond_angle_DHA _geom_hbond_publ_flag C3 H3 F3 1_665 0.95 2.43 3.137(2) 131 y C7 H7 F1 2_576 0.95 2.54 3.378(2) 148 y C12 H12 F2 . 0.95 2.42 3.192(2) 138 y data_global _journal_data_validation_number ? _journal_date_recd_electronic 2011-10-24 _journal_date_accepted 2011-10-26 _journal_name_full 'Acta Crystallographica, Section E' _journal_year 2011 _journal_volume 67 _journal_issue 11 _journal_page_first o3108 _journal_page_last o3108 _journal_paper_category QO _journal_coeditor_code SU2336 _publ_contact_author_name 'Dr. Mohammad Khaledi' _publ_contact_author_address ; Department of Chemistry, Faculty of Science, Islamic Azad University, Shahrekord Branch Box 166, Iran ; _publ_contact_author_email khaledi1974@yahoo.com _publ_contact_author_fax '+98-' _publ_contact_author_phone '+98-' _publ_section_title ;\ (E,E)-N^1^,N^4^-Bis(2,6-difluorobenzylidene)butane-\ 1,4-diamine ; loop_ _publ_author_name _publ_author_address 'Khaledi, Mohammad' ; Department of Chemistry Faculty of Science Islamic Azad University Shahrekord Branch Box 166 Tehran Iran ; 'Kia, Reza' ; Department of Chemistry Science and Research Branch Islamic Azad University Tehran Iran ; 'Clegg, William' ; School of Chemistry Newcastle University Newcastle upon Tyne NE1 7RU England ; 'Harrington, Ross W.' ; School of Chemistry Newcastle University Newcastle upon Tyne NE1 7RU England ;