Studies On The Synthesis, Structure And Properties Of Metal-organic Frameworks Bearing N-toluene Sulfonyl-s-carboxymethyl-l-cysteine

Metal-organic frameworks constructed from metal ions and organic ligands exhibit much advantage over zeolites such as gas absorption, catalysis, magnetism, optical properties. Rigid multidentate organic carboxylaic acids were widely used as linkers in the reported MOFs. Much less was concerned about flexible linkers. However the MOFs built from flexible ligands is drawing more and more attention for the size and shape of its pore are tunable. In this thesis we aimed to synthesize a flexible ligand of N-sulfonyl–S -Carboxymethyl -L-Cysteine containing multi-coordination sites and to construct novel MOFs using it as linkers. We report here the structures and fluorescent properties of eleven complexes which were characterized by IR spectroscopy, elemental analysis and single crystal X-ray diffraction analysis.1. The reactions of Co(OAc)₂·4H₂O or Ni(OAc)₂·2H₂O with N-sulfonyl-S-Carboxy methyl-L-Cysteine in the absence or presence of an ancillary ligand gave four complexes [Co(ts-scmc)(H₂O)3]·H₂O (1), [Ni(ts-scmc)(H₂O)3]·H₂O (2), [Co(phen)(ts-scmc)(H₂O)]·H₂O (3), [Co(2,2'-bipy)(ts-scmc)(H₂O)]·H₂O (4), respectively. Complex (1) crystallizes in the monoclinic space group P21 with a = 9.893(3) A, b = 5.2512(16) A, c = 18.430(6) A. The Co(II) ion in complex (1) is six-coordinated in a distorted octahedral geometry. Complex (2) crystallizes in the monoclinic space group P21 with a = 9.806(2) A, b = 5.2563(11) A, c = 18.278(4) A. The Ni(II) ion in complex (2) is six-coordinated in a distorted octahedral geometry. Complex (3) crystallizes in the orthorhombic space group P212121 with a = 7.6935(7) A, b = 16.4484(15) A, c = 19.2891(18) A. The Co(II) ion in complex (3) is six-coordinated in a distorted octahedral geometry. Complex (4) crystallizes in the monoclinic space group P21 with a = 10.4107(12) A, b = 7.8553(10) A, c= 27.677(3) A. The Co(II) ion in complex (4) in six-coordinated in a distorted octahedral geometry. The ts-scmc ligand in the reaction of preparing complexes (3) and (4) decomposed into N-sulfonyl-L-cysteic acid due to the high pH value of 8.2. The reactions of Cd(OAc)₂·6H₂O with N-sulfonyl-S-Carboxymethyl-L-Cysteine in the absence or presence of an ancillary ligand provided three coordination polymers [Cd(ts-scmc)]n (5), [Cd(ts-scmc)(4,4'-bipy)(H₂O)]n (6), [Cd(ts-scmc)(Im)(H₂O)]n (7). Complex (5) crystallizes in the monoclinic space group P21 with a = 8.5289(15) A, b = 6.0505(10) A, c = 14.924(2) A. The Cd(II) ion in complex (5) is six-coordinated in a distorted octahedral geometry. The two carboxylate groups of the S-Carboxymethyl-L-Cysteine in this complex present different coordination modes. The carboxylate group in–S-CH2-COO– part adopts aμ3,η3–bridging mode connecting three Cd(II) ions, while the other one in–CH2CH(NH2)COO– part adopts aμ2,η2–coordination mode connecting two Cd(II) ions. The Cd(II) ions are connected alternatively by the two kinds of carboxylato groups leading to the construction of a 2D network with 1D chiral helical channels. Complex (6) crystallizes in the monoclinic space group P21 with a = 10.7419(8) A, b = 11.0361(8) A, c = 11.7804(9) A. The Cd(II) ion in complex (6) is seven-coordinated. Two carboxylato groups of ts-scmc ion chelate to two Cd(II) ions, respectively, resulting in the formation of 1D chains which further brideged by 4,4'-bipy to form 2-D network. There are Hydrogen bonds help to construct a supramolecular 3D network. Complex (7) crystallizes in the monoclinic space group P21 with a = 10.543(7) A, b = 4.990(3) A, c = 18.508(13) A. The Cd(II) ion in complex (7) is six coordinated.. Two carboxylato groups of the S-Carboxymethyl-L- Cysteine in this complex present different coordination modes: chelating and bidentate coordination modes. The Cd(II) ions are bridged by ts-scmc build a 1D channel. We investigated the photoluminescent properties of complexes (5), (6) and (7). All of the emissions in these complexes might be assigned to intraligand fluorescent emissions. The fluorescent intensities of compounds (5), (6), (7) are stronger than those of the free ligands.3. The reactions of Zn(OAc)₂·2H₂O or Mn(OAc)₂·4H₂O with N-sulfonyl-S-Carboxy methyl-L-Cysteine as the main starting materials provided [Zn2(ts-scmc)2(4,4'-bipy)2(H₂O)2]n (8), [Zn(ts-scmc)(Im)(H₂O)]n (9), [Zn2(ts-scmc)2(2,2'-bipy)2(H₂O)2]·2H₂O (10), [Mn(ts-scmc)(4,4'- bipy)(H₂O)]n (11). Complex (8) crystallizes in the monoclinic space group P21 with a = 11.4808(14) A, b = 10.6735(13) A, c = 19.985(2) A. All of the Zn(II) ions in complex (8) are six-coordinated. The carboxylate groups bridge adjacent metals to form 1D chains which are further bridged by 4,4'-bpy forming 2D network grid structure. The 2D networks are further connected by abundant hydrogen bonds to form a 3D supramolecular network. Complex (9) crystallizes in the orthorhombic space group P212121 with a = 5.0605(8) A, b = 10.4608(17) A, c = 36.916(6) A. The Zn(II) ion in complex (9) is five-coordinated. The ts-scmc ligand in complex (9) behaves as a bidentate bridging ligand with each carboxylato group acting as a monodentate coordination mode, resulting in the formation of 1-D channel. Hydrogen bonds connect the 1D channels into a 2D network. Complex (10) crystallizes in the monoclinic space group C2 with a = 26.545(4) A, b = 6.8628(10) A, c = 17.018(3) A,β= 120.680(2)°. The Zn(II) ions in complex (10) are also five-coordinated. Two Zn(II) are bridged by two ts-scmc ligands to form a dinuclear molecule. Complex (11) crystallizes in the monoclinic space group P21 with a = 5.382(4) A, b = 19.375(14) A, c= 11.691(9) A,β= 96.771(9)°. The Mn(II) ions in in complex (11) are six-coordinated. The Mn(II) ions in complex (11) are bridged by ts-scmc to form a 2D network which are further bridged by 4,4'-bpy to form a 3-D structure. The photoluminescent properties of complexes (8) and (9) were investigated. The stronger emission bands can probably be assigned to intraligand fluorescent emissions. The fluorescent intensity of compound (9) is stronger than compound (8).In these complexes N-sulfonyl- S-Carboxymethyl-L-Cysteine shows versatile coordination modes when coordinating to transition metals. The introduction of ancillary ligands such as 4,4'-bipy, Im, Phen and 2,2'-bipy leads to a much more intensive study in this system.