Packianathan Thomas Muthiah

Nickel and cobalt complexes of benzoic acid (2-hydroxy-benzylidene)-hydrazide ligand: synthesis, structure and comparative in vitro evaluations of biological perspectives

Reactions of tridentate chelating hydrazone Schiff bases benzoic acid (2-hydroxyl-benzylidene)-hydrazide (H2L) (1) obtained from salicylaldehyde and benzhydrazide with [NiCl2(PPh3)2] and [CoCl2(PPh3)2] afforded respective metal hydrazone complexes of the composition [Ni(L)(PPh3)] (2) and [Co1(L)2]2[Co2(H2O)4(OPPh3)2] (3). The molecular structure of both complexes 2 and 3 determined by single crystal X-ray diffraction revealed that complex 2 is neutral in charge with distorted square planar geometry. However, complex 3 was found to have distorted octahedral geometry. All of the synthesised compounds 1–3 were studied by interaction with calf thymus DNA (CT DNA) and bovine serum albumin (BSA). In addition in vitro free radical scavenging and cytotoxic potential of all the synthesised compounds were also investigated.

Metal-nucleobase interactions: Synthesis and crystal structure of trichlorobis(N6-benzyl adeninium) copper(II) chloride dihydrate

The crystal structure of trichlorobis(N6-benzyl adeninium)copper(II) chloride dihydrate has been investigated to explore the relation among site of protonation, mode/site of coordination, and conformation of the substituent in the adenine system, which is one of the major bases of nucleic acids. Space group: P21/c, a = 10.713(9), b = 21.214(12), c = 13.560(10) A, β = 110.52(6)°, R = 0.0512. Three chloride ions and two benzyl adeninium cations [coordinating through (N9)] complete the trigonal bipyramidal coordination sphere around copper. There are two water molecules of crystallization and a chloride ion, which are not coordinated to the metal, but held in the lattice by the network of hydrogen bonding. The N6 substituent is distal to the imidazole nitrogen as reported for N6 substituted adenines. Both of the adenine moieties are protonated at N(3) in addition to N(7), which is rather unusual and very interesting, whereas under normal situations in adenine, N(1) is the preferred site of protonation. The dihedral angles between the adenine and benzene groups in the ligands are 100.2(2)° and 92.7(2)°, which is close to 90°, as expected for active cytokinins.

Pseudo-polymorphism and crystal engineering: hydrogen-bonded supramolecular networks in trimethoprim m-chlorobenzoate and trimethoprim m-chlorobenzoate dihydrate

This manuscript deals with the crystal structures of two pseudo-polymorphic forms, namely, trimethoprim m-chlorobenzoate (1) and trimethoprim m-chlorobenzoate dihydrate (2). In both the structures, the pyrimidine moieties of trimethoprim are protonated at one of the ring nitrogens. In both the forms, the carboxylate group interacts with the protonated pyrimidine ring to form the cyclic hydrogen-bonded bimolecular motif. These motifs are further self-organized into two different hydrogen-bonded networks. In compound 1, two of the centrosymmetrically-related motifs are hydrogen-bonded to give a complementary DDAA (D refers to the hydrogen bond donor and A refers to the hydrogen bond acceptor) array of quadruple hydrogen bonding pattern. In compound 2, two of the inversion-related motifs are paired through a pair of N–H⋯N hydrogen bonds involving the 2-amino group and the N3 atom. In addition to the pairing, one water molecule bridges the 4-amino group of one motif and the carboxylate oxygen of another motif on both sides of the pairing, leading to a complementary linear array of hydrogen bonds.

N6-furfuryladenine (kinetin) hydrochloride.

In the title compound, N(6)-furfuryladenin-3-ium chloride, C(10)H(10)N(5)O(+).Cl(-), the adenine moiety exists as the N3-protonated N7-H tautomer. The orientation of the N6 substituent (furfuryl moiety) is distal to the imidazole ring of the adenine base. The dihedral angle between the adenine plane and the furfuryl ring plane is 76.1 (2) degrees. Three N-H...Cl hydrogen bonds are responsible for the formation of a supramolecular chain-like pattern. These supramolecular chains are interconnected by C-H...Cl hydrogen bonds to form a hydrogen-bonded sheet and a three-dimensional hydrogen-bonded network.

Design of co-crystals/salts of some Nitrogenous bases and some derivatives of thiophene carboxylic acids through a combination of hydrogen and halogen bonds

BackgroundThe utility of N-heterocyclic bases to obtain molecular complexes with carboxylic acids is well studied. Depending on the solid state interaction between the N-heterocyclic base and a carboxylic acid a variety of neutral or ionic synthons are observed. Meanwhile, pyridines and pyrimidines have been frequently chosen in the area of crystal engineering for their multipurpose functionality. HT (hetero trimers) and LHT (linear heterotetramers) are the well known synthons that are formed in the presence of pyrimidines and carboxylic acids.ResultsFourteen crystals involving various substituted thiophene carboxylic acid derivatives and nitrogenous bases were prepared and characterized by using single crystal X-ray diffraction. The 14 crystals can further be divided into two groups [1a-7a], [8b-14b] based on the nature of the nitrogenous base. Carboxylic acid to pyridine proton transfer has occurred in 3 compounds of each group. In addition to the commonly occurring hydrogen bond based pyridine/carboxylic acid and pyrimidine/carboxylic acid synthons which is the reason for assembly of primary motifs, various other interactions like Cl…Cl, Cl…O, C–H…Cl, C-H…S add additional support in organizing these supermolecules into extended architectures. It is also interesting to note that in all the compounds π-π stacking occurs between the pyrimidine-pyrimidine or pyridine-pyridine or acid-acid moieties rather than acid-pyrimidine/pyridine.ConclusionsIn all the compounds (1a-14b) either neutral O–H…Npyridyl/pyrimidine or charge-assisted Npyridinium-H…Ocarboxylate hydrogen bonds are present. The HT (hetero trimers) and LHT (linear heterotetramers) are dominant in the crystal structures of the adducts containing N-heterocyclic bases with two proton acceptors (1a-7a). Similar type supramolecular ladders are observed in 5TPC44BIPY (8b), TPC44BIPY (9b), TPC44TMBP (11b). Among the seven compounds [8b-14b] the extended ligands are linear in all except for the TMBP (10b, 11b, 12b). The structure of each compound depends on the dihedral angle between the carboxyl group and the nitrogenous base. All these compounds indicate three main synthons that regularly occur, namely linear heterodimer (HD), heterotrimer (HT) and heterotetramer (LHT).

R22(8) motifs in Aminopyrimidine sulfonate/carboxylate interactions: Crystal structures of pyrimethaminium benzenesulfonate monohydrate (2:2:1) and 2-amino-4,6-dimethylpyrimidinium sulfosalicylate dihydrate (4:2:2)

BackgroundPyrimethamine [2,4-diamino-5-(p-chlorophenyl)-6-ethylpyrimidine] is an antifolate drug used in anti-malarial chemotherapy. Pyrimidine and aminopyrimidine derivatives are biologically important compounds owing to their natural occurrence as components of nucleic acids.ResultsIn the crystal structures of two organic salts, namely pyrimethaminium benzenesulfonate monohydrate 1 and 2-amino-4, 6-dimethylpyrimidinium 3-carboxy-4-hydroxy benzenesulfonate dihydrate 2, pyrimethamine (PMN) and 2-amino-4,6-dimethylpyrimidine (AMPY) are protonated at one of the nitrogens in the pyrimidine rings. In both the PMN and AMPY sulfonate complexes, the protonated pyrimidine rings are hydrogen bonded to the sulfonate groups, forming a hydrogen-bonded bimolecular ring motif with graph-set notation R22(8). The sulfonate group mimics the carboxylate anions mode of association, which is more commonly seen when binding with 2-aminopyrimidines. In compound 1, the PMN moieties are centrosymmetrically paired through a complementary DADA array of hydrogen bonds. In compound 2, two types of bimolecular cyclic hydrogen bonded R22(8) motifs (one involving the carboxylate group and the other involving sulfonate group) coexist. Furthermore, this compound is stabilized by intra and intermolecular O-H...O hydrogen bonds.ConclusionThe crystal structures of pyrimethaminium benzenesulfonate monohydrate and 2-amino-4,6-dimethylpyrimidinium sulfosalicylate dihydrate have been investigated in detail. In compound 1, the R22(8) motif involving the sulfonate group is present. The role the sulfonic acid group plays in mimicking the carboxylate anions is thus evident. In compound 2, two types of bimolecular cyclic hydrogen bonded R22(8) motifs (one involving the carboxylate group and the other involving sulfonate group) coexist. In both the compounds base pairing also occurs. Thus homo and hetero synthons are present.

Syntheses, characterization, and supramolecular architectures of two lead(II) complexes of 8-quinolinol

Two Pb(II) complexes with 8-quinolinol (8-Quin), 5-chloro thiophene-2-carboxylic acid, and (5-CTPC)/5-bromo thiophene-2-carboxylic acid (5-BTPC) have been synthesized and characterized by IR, 13C NMR, and solid state photoluminescence spectra. The structures of [Pb(8-Quin)4](5-CTPC)2 (1) and [Pb(8-Quin)2(8-Quio)](5-BTPC) (2) [(8-Quio) = 8-quinolinolate] have been confirmed by X-ray crystallography. Both complexes crystallize in the triclinic crystal system with a space group . In 1, Pb(II) is eight coordinate by four bidentate 8-quinolinol groups, while in 2 it is six coordinate by two bidentate 8-quinolinol groups and one bidentate 8-quinolinolate group. This leads to square antiprismatic and pentagonal pyramidal geometries around Pb(II) in 1 and 2, respectively. Two of the 5-CTPC ligands in 1 and a 5-BTPC in 2 are involved in strong O–H···O hydrogen bonding in the lattice. Cl···π interactions are found in 1. The crystal structures are stabilized by weak C–H···O and π–π stacking interactions.

Amino­pyrimidine–carboxyl­(ate) interactions in trimethoprim maleate, an antifolate drug

In the title cocrystal, trimethoprim maleate [2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidin-1-ium maleate], C(14)H(19)N(4)O(3)(+).C(4)H(3)O(4)(-), the trimethoprim molecule is protonated at N1. The carboxyl group of the maleate ion makes a specific double hydrogen bond of type N-H.O with the 2-amino group and the protonated N1 atom of the trimethoprim cation which is similar to the carboxylate-trimethoprim cation interaction observed in the complex of dihydrofolate reductase with trimethoprim. The pyrimidine moieties of trimethoprim cations are centrosymmetrically paired through a pair of N-H.N hydrogen bonds involving the 4-amino group and the pyridinium N3 atom of a symmetry-related molecule. One of the O atoms at the maleate carboxylate group bridges the 2-amino and 4-amino groups on either side of the paired trimethoprim cations. The other O atom of the carboxylate group forms an intramolecular O-H.O hydrogen bond with the carboxyl group. These characteristic hydrogen bonds result in infinite two-dimensional aggregation of rings into a supramolecular ladder, which is further crosslinked through weak C-H.O interactions with methoxy groups of neighbouring trimethoprim molecules to form a layered structure.

Supramolecular architectures and structural diversity in a series of lead (II) Chelates involving 5-Chloro/Bromo thiophene-2-carboxylate and N,N’-donor ligands

BackgroundLead is a heavy toxic metal element in biological systems and is one of the major pollutants as a result of its widespread use in industries. In spite of its negative roles the coordination chemistry of Pb(II) complexes is a matter of interest. The N,N’-bidentate aromatic bases such as BPY,4-BPY and PHEN (BPY = 2,2′bipyridine, 4-BPY = 4,4′-dimethyl-2,2′-bipyridine, PHEN = 1,10-Phenanthroline) are widely used to build supramolecular architectures because of their excellent coordinating ability and large conjugated system that can easily form π-π interactions among their aromatic moieties. A series of novel Pb(II) complexes in concert with 5-CTPC, 5-BTPC (5-CTPC = 5-chlorothiophen-2-carboxylate, 5-BTPC = 5-bromothiophen-2-carboxylate) and corresponding bidentate chelating N.N′ ligands have been synthesized and characterized.ResultsFive new Pb (II) complexes [Pb(BPY)(5-CTPC)2] (1), [Pb(4-BPY)(5-CTPC)2] (2), [Pb2(PHEN)2(5-CTPC)4] (3), [Pb(4-BPY)(5-BTPC)2] (4) and [Pb2(PHEN)2(5-BTPC)2(ACE)2] (5) have been synthesized. Even though in all these complexes the molar ratio of Pb, carboxylate, N,N-chelating ligand are the same (1:2:1), there is a significant structural diversity. These complexes have been characterised and investigated by elemental analysis, IR, 1H-NMR,13C-NMR, TGA, and photoluminescence studies. Single crystal X-ray diffraction studies reveal that complexes (1, 2) and (4) are mononuclear while (3 and 5) are dinuclear in nature which may result from the chelating nature of the ligands, various coordination modes of the carboxylates, and the coordination geometry of the Pb(II) ions.ConclusionsThe observation of structures 2,4 and 3,5 show the structural changes made just chloro/bromo substituent of the thiophene ring. A detailed packing analysis has been undertaken to delineate the role of valuable non covalent interactions like X…π, H…X, (X = Cl/Br). A quadruple hydrogen bond linking the monomeric units and generating a supramolecular architecture is observed in (1). The metal bite unit comprised of PbN2C2 (i.e. Pb-N-C-C-N-Pb) is the repeating unit in all the five complexes and they have almost same geometrical parameters. This metal bite has been identified as the self assembly unit in complexes.

Hydrogen‐bonded supramolecular motifs in 2‐amino‐4,6‐dimethoxypyrimidinium 4‐hydroxybenzoate monohydrate, 2‐amino‐4,6‐dimethoxypyrimidinium 6‐carboxypyridine‐2‐carboxylate monohydrate and 2‐amino‐4,6‐dimethoxypyrimidinium hydrogen (2R,3R)‐tartrate 2‐amino‐4,6‐dimethoxypyrimidine

In the crystal structures of the title compounds, C(6)H(10)N(3)O(2)+.C(7)H(5)O(3)-.H2O, (I), C(6)H(10)N(3)O(2)+.C(7)H(4)NO(4)-.H2O, (II), and C(6)H(10)N(3)O(2)+.C(4)H(5)O(6)-.C(6)H(9)N(3)O(2), (III), the 2-amino-4,6-dimethoxypyrimidinium cation [abbreviated as (MeO)2-Hampy+] interacts with the carboxylate group of the corresponding anion through a pair of nearly parallel N-H...O hydrogen bonds to form R(2)(2)(8) ring motifs. In (I), the (MeO)2-Hampy+ cation is centrosymmetrically paired through a pair of N-H...N hydrogen bonds involving the 2-amino group and a ring N atom forming an R(2)(2)(8) motif. In (II), inversion-related R(2)(2)(8) motifs (amino-pyrimidine-carboxylate motifs) are further bridged by N-H...O hydrogen bonds on either side forming a DDAA array of quadruple hydrogen bonds. This array is extended further on either side by O(water)-H...O(methoxy) hydrogen bonds, resulting in an array of six hydrogen bonds (ADDAAD). The water molecule plays a pivotal role, and five hydrogen-bonded fused rings are formed around the water molecule. In (III), the carboxy group of the tartrate anion interacts with the ring N atom and 2-amino group of the neutral (MeO)2-ampy molecule through N-H...O and O-H...N hydrogen bonds. There is also an intramolecular O-H...O hydrogen bond in the tartrate anion. In all three crystal structures, C-H...O hydrogen bonds are observed.