Change search
Link to record
Permanent link

Direct link
BETA
George, Sumod
Publications (10 of 24) Show all publications
Alhalaweh, A., George, S., Basavoju, S., Childs, S., Rizvi, S. & Velaga, S. (2012). Pharmaceutical cocrystals of nitrofurantoin: Screening, characterization and crystal structure analysis (ed.). Paper presented at . CrystEngComm, 14(15), 5078-5088
Open this publication in new window or tab >>Pharmaceutical cocrystals of nitrofurantoin: Screening, characterization and crystal structure analysis
Show others...
2012 (English)In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 14, no 15, p. 5078-5088Article in journal (Refereed) Published
Abstract [en]

The objective of this study was to screen and prepare cocrystals of the poorly soluble drug nitrofurantoin (NTF) with the aim of increasing its solubility. Screening for cocrystals of NTF using 47 coformers was performed by high-throughput (HT) screening using liquid assisted grinding (LAG) methods. Raman spectroscopy and powder X-ray diffraction (PXRD) were used as the primary analytical tools to identify the new crystalline solid forms. Manual LAG and reaction crystallization (RC) experiments were carried out to confirm and scale-up the hits. Seven hits were confirmed to be cocrystals. The cocrystals were characterized by PXRD, Raman and IR spectroscopy, thermal analysis (DSC and TGA) and liquid-state NMR or elemental analysis. The solution stability of the scaled-up cocrystals in water was tested by slurrying the cocrystals at 25 °C for one week. NTF forms cocrystals with a 1:1 stoichiometric ratio with urea (1), 4-hydroxybenzoic acid (2), nicotinamide (3), citric acid (4), l-proline (5) and vanillic acid (6). In addition, NTF forms a 1:2 cocrystal with vanillin (7). All but one of the NTF cocrystals transformed (dissociated) in water, resulting in NTF hydrate crystalline material or NTF hydrate plus the coformer, which indicates that the transforming cocrystals have a higher solubility than the NTF hydrate under these conditions. The crystal structures of 1:1 NTF-citric acid (4) and 1:2 NTF-vanillin (7) were solved by single-crystal X-ray diffraction. The crystal structures of these two cocrystals were analyzed in terms of their supramolecular synthons.

National Category
Other Health Sciences
Research subject
Health Science
Identifiers
urn:nbn:se:ltu:diva-3653 (URN)10.1039/c2ce06602e (DOI)000305999500030 ()2-s2.0-84863691005 (Scopus ID)17841dce-6928-461f-a2e5-a264c058b889 (Local ID)17841dce-6928-461f-a2e5-a264c058b889 (Archive number)17841dce-6928-461f-a2e5-a264c058b889 (OAI)
Note
Validerad; 2012; 20120806 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Alhalaweh, A., George, S., Boström, D. & Velaga, S. (2010). 1:1 and 2:1 urea-succinic acid cocrystals: structural diversity, solution chemistry, and thermodynamic stability (ed.). Paper presented at . Crystal Growth & Design, 10(11), 4847-4855
Open this publication in new window or tab >>1:1 and 2:1 urea-succinic acid cocrystals: structural diversity, solution chemistry, and thermodynamic stability
2010 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, no 11, p. 4847-4855Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to study the crystal structures of 1:1 and 2:1 urea-succinic acid (U-SA) cocrystals and to investigate the role of solution chemistry in the formation and stability of different stoichiometric cocrystals. The structural diversity of other urea-dicarboxylic acid cocrystals is also discussed. The 1:1 U-SA cocrystal was stabilized by an acid-amide heterosynthon while acid-amide heterosynthons and amide-amide homosynthons stabilized the 2:1 cocrystals. The hydrogen bonding motifs in 1:1 and 2:1 U-SA cocrystals were consistent with other urea-dicarboxylic acid systems with similar stoichiometries. The 1:1 cocrystals were transformed to 2:1 cocrystals upon slurrying in various solvents at 25 °C. The phase solubility diagram was used to define the stability regions of different solid phases in 2-propanol at 25 °C. While no phase stability region for 1:1 cocrystal could be found, the stable regions for the 2:1 cocrystals and their pure components were defined by eutectic points. The solubility of the 2:1 cocrystals was dependent on the concentration of the ligand in the solution and explained by the solubility product and 1:1 solution complexation. The mathematical models predicting the solubility of the 2:1 cocrystals were evaluated and found to fit the experimental data

National Category
Other Health Sciences
Research subject
Health Science
Identifiers
urn:nbn:se:ltu:diva-7441 (URN)10.1021/cg100823p (DOI)2-s2.0-78149347394 (Scopus ID)5d1ce560-f622-11df-8b95-000ea68e967b (Local ID)5d1ce560-f622-11df-8b95-000ea68e967b (Archive number)5d1ce560-f622-11df-8b95-000ea68e967b (OAI)
Note
Validerad; 2010; 20101122 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Reddy, L. S., Chandran, S. K., George, S., Babu, N. J. & Nangia, A. (2007). Crystal Structures of N-Aryl-N′-4-Nitrophenyl Ureas: Molecular Conformation and Weak Interactions Direct the Strong Hydrogen Bond Synthon (ed.). Paper presented at . Crystal Growth & Design, 7(12), 2675-2690
Open this publication in new window or tab >>Crystal Structures of N-Aryl-N′-4-Nitrophenyl Ureas: Molecular Conformation and Weak Interactions Direct the Strong Hydrogen Bond Synthon
Show others...
2007 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 7, no 12, p. 2675-2690Article in journal (Refereed) Published
Abstract [en]

Hydrogen bond competition was studied in 21 X-ray crystal structures of N-X-phenyl-N′-p-nitrophenyl urea compounds (X = H, F, Cl, Br, I, CN, C≡CH, CONH2, COCH3, OH, Me). These structures are classified into two families depending on the hydrogen bond pattern: urea tape structures contain the well-known α-network assembled via N-HO hydrogen bonds; however, in nonurea tape structures the N-H donors hydrogen bond with NO2 groups or solvent O acceptor atoms. Surprisingly, the urea CO hardly accepts strong H bonds in nonurea type structures sustained by ureanitro and ureasolvent synthons. The carbonyl group accepts intra- and intermolecular C-HO interactions. The molecular conformation and H bonding motifs are different in the two categories of structures: the phenyl rings are twisted out of the urea plane in the tape motif, but they are coplanar in the nonurea category. Even though hydrogen bond synthon energy and urea carbonyl acceptor strength favor the N-HO tape structure, the dominant pattern in electron-withdrawing aryl urea crystal structures is the ureanitro/ureasolvent synthon and persistence of intramolecular C-HO interactions. Remarkably, the presence of functional groups that can promote specific C-IO or C-HO interactions with the interfering NO2 group, for example, when X = I, C≡CH, NMe2, and Me, steers crystallization toward the N-HO urea tape structure, and now the diaryl urea molecule adopts the metastable, twisted conformation. Molecular conformer energy calculations and difference nuclear Overhauser enhancement NMR experiments show that the planar, trans-trans-N,N′-diphenyl urea conformation is more stable than the N-Ph twisted rotamer. However, the urea CO is a better hydrogen bond acceptor in the twisted conformer compared to the planar one, based on electrostatic surface potential (ESP) charges. These diaryl ureas together with previously reported crystal structures provide a global structural model to understand how functional groups, molecular conformation, hydrogen bonding, and crystal packing are closely related and influence each other in subtle yet definitive ways. Our strategy simultaneously exploits weak, soft intermolecular interactions and strong, hard hydrogen bonds [supramolecular hard and soft acid-base (HSAB) principle] in the crystal engineering of multifunctional molecules.

Identifiers
urn:nbn:se:ltu:diva-7257 (URN)10.1021/cg070155j (DOI)599c9b50-07ba-11dd-97e0-000ea68e967b (Local ID)599c9b50-07ba-11dd-97e0-000ea68e967b (Archive number)599c9b50-07ba-11dd-97e0-000ea68e967b (OAI)
Note
Upprättat; 2007; 20080411 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Lipstman, S., Muniappan, S., George, S. & Goldberg, I. (2007). Framework coordination polymers of tetra(4-carboxyphenyl)porphyrin and lanthanide ions in crystalline solids (ed.). Paper presented at . Dalton Transactions (30), 3273-3281
Open this publication in new window or tab >>Framework coordination polymers of tetra(4-carboxyphenyl)porphyrin and lanthanide ions in crystalline solids
2007 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 30, p. 3273-3281Article in journal (Refereed) Published
Abstract [en]

Targeted synthesis of framework coordination polymers was achieved by reacting meso-tetra(4-carboxyphenyl)porphyrin with common salts of lanthanide metal ions. The large size, high coordination numbers and strong affinity for oxo ligands of the latter, combined with favourable hydrothermal reaction conditions in acidic environments, allowed the formation of open three-dimensional single-framework architectures in which the tetra-dentate porphyrin units are inter-coordinated by multinuclear assemblies of the bridging metal ions, which serve as construction pillars, into infinite architectures. Three different modes of coordination polymerisation were characterized by single-crystal X-ray diffraction. They differ by the nuclearity of the metal connectors. All structures exhibit, however, layered organization of the porphyrin-metal domains, and periodically spaced solvent accessible channel voids that penetrate through these layers throughout the corresponding crystals. Thermal analysis provided additional insight into the stability of these polymeric materials.

Identifiers
urn:nbn:se:ltu:diva-8862 (URN)10.1039/b703698a (DOI)769cda60-07bc-11dd-97e0-000ea68e967b (Local ID)769cda60-07bc-11dd-97e0-000ea68e967b (Archive number)769cda60-07bc-11dd-97e0-000ea68e967b (OAI)
Note
Upprättat; 2007; 20080411 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Muniappan, S., Lipstman, S., George, S. & Goldberg, I. (2007). Porphyrin framework solids: synthesis and structure of hybrid coordination polymers of tetra(carboxyphenyl)porphyrins and lanthanide-bridging ions (ed.). Paper presented at . Inorganic Chemistry, 46(14), 5544-5554
Open this publication in new window or tab >>Porphyrin framework solids: synthesis and structure of hybrid coordination polymers of tetra(carboxyphenyl)porphyrins and lanthanide-bridging ions
2007 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, no 14, p. 5544-5554Article in journal (Refereed) Published
Abstract [en]

New types of porphyrin-based framework solids were constructed by reacting meso-tetra(3-carboxyphenyl)porphyrin and meso-tetra(4-carboxyphenyl)metalloporphyrins with common salts of lanthanide metal ions. The large size, high coordination numbers and strong affinity for oxo ligands of the latter, combined with favorable hydrothermal reaction conditions, allowed the formation of open three-dimensional single-framework architectures by coordination polymerization, in which the tetradentate porphyrin units are intercoordinated by multinuclear assemblies of the bridging metal ions. The latter serve as construction pillars of the supramolecular arrays, affording stable structures. Several modes of coordination polymerization were revealed by single-crystal X-ray diffraction. They differ by the spatial functionality of the porphyrin building blocks, the coordination patterns of the lanthanide-carboxylate assemblies, and the topology of the resulting frameworks. The seven new reported structures exhibit periodically spaced 0.4-0.6 nm wide channel voids that perforate the respective crystalline polymeric architectures and are accessible to solvent components. Materials based on the m-carboxyphenyl derivative reveal smaller channels than those based on the p-carboxyphenyl analogues. An additional complex of the former with a smaller third-row transition metal (Co) is characterized by coordination connectivity in two dimensions only. Thermal and powder-diffraction analyses confirm the stability of the lanthanide-TmCPP (TmCPP = tetra(m-carboxyphenyl)porphyrin) frameworks.

Identifiers
urn:nbn:se:ltu:diva-12461 (URN)10.1021/ic0701099 (DOI)b9d3d4a0-07b7-11dd-97e0-000ea68e967b (Local ID)b9d3d4a0-07b7-11dd-97e0-000ea68e967b (Archive number)b9d3d4a0-07b7-11dd-97e0-000ea68e967b (OAI)
Note
Upprättat; 2007; 20080411 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Lipstman, S., George, S. & Goldberg, I. (2006). (4-Acetyl­pyridine)(tetra­phenyl­porphyrinato)zinc(II) (ed.). Paper presented at . Acta Crystallographica Section E: Structure Reports Online, 62(3), m417-m419
Open this publication in new window or tab >>(4-Acetyl­pyridine)(tetra­phenyl­porphyrinato)zinc(II)
2006 (English)In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 62, no 3, p. m417-m419Article in journal (Refereed) Published
Abstract [en]

The title compound, [Zn(C44H28N4)(C7H7NO)], is a square-pyramidal five-coordinate zinc-porphyrin complex with γ-acetyl­pyridine as the apical ligand. The inter­molecular packing involves van der Waals forces, close π-π stacking and C-Hπ contacts, revealing an inter­esting pairing of adjacent mol­ecules related by inversion.

Identifiers
urn:nbn:se:ltu:diva-12971 (URN)10.1107/S1600536806003527 (DOI)c1ea4dc0-06dd-11dd-97e0-000ea68e967b (Local ID)c1ea4dc0-06dd-11dd-97e0-000ea68e967b (Archive number)c1ea4dc0-06dd-11dd-97e0-000ea68e967b (OAI)
Note
Upprättat; 2006; 20080410 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
George, S., Lipstman, S., Muniappan, S. & Goldberg, I. (2006). Porphyrin network solids: examples of supramolecular isomerism, noncentrosymmetric architectures and competing solvation (ed.). Paper presented at . CrystEngComm, 8(5), 417-424
Open this publication in new window or tab >>Porphyrin network solids: examples of supramolecular isomerism, noncentrosymmetric architectures and competing solvation
2006 (English)In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 8, no 5, p. 417-424Article in journal (Refereed) Published
Abstract [en]

Self-assembly of functionalized tetraarylporphyrins into 2-D and 3-D supramolecular arrays may exhibit structural isomerism when carried out in different experimental conditions. This study shows that the open 2-D hydrogen bonding quadrangular grid networks of free-base tetra(4-carboxyphenyl)porphyrin (TCPP) form an interweaved crystalline architecture, in addition to the non-interweaved offset-stacked porous arrangement observed before. In the two structures the individual arrays are similarly stabilized by multiple cyclic-dimeric (COOH)2 hydrogen bonding synthons, differing slightly in the grid shape. The Mn-metalled TCPP building blocks afford in a lipophilic environment 2-D coordination polymers by direct Mn-OOC/HOOC association between the tetra-acid metalloporphyrin units, without incorporation of any external bridging auxiliaries. This polymerization is further enforced by interporphyrin O-HO hydrogen bonding within and between the 2-D arrays, yielding a solvent-free 3-D architecture. The latter is related to an isomeric crystalline organization of similar layered Mn-TCPP coordination polymers obtained earlier from hydrophilic crystallization mixtures, wherein intercalated solvent separates the layered polymeric arrays. The non-acidic Mn(Cl)-TOHPP compound yields a chiral 3-D assembly sustained by multiple inter-porphyrin hydrogen bonding. Its formation is promoted by the non-centrosymmetric (axially polarized) shape of this porphyrin unit, as well as by the directional hydrogen bonding interactions, and it involves coordination of an additional axial ligand to the manganese ion. Effects of competing solvation, which interfere with the supramolecular aggregation of the TCPP scaffolds into network arrays, are demonstrated also by structures obtained from solvent mixtures containing dimethylsulfoxide.

Abstract [sv]

Self-assembly of functionalized tetraarylporphyrins into 2-D and 3-D supramolecular arrays may exhibit structural isomerism when carried out in different experimental conditions. This study shows that the open 2-D hydrogen bonding quadrangular grid networks of free-base tetra(4-carboxyphenyl)porphyrin (TCPP) form an interweaved crystalline architecture, in addition to the non-interweaved offset-stacked porous arrangement observed before. In the two structures the individual arrays are similarly stabilized by multiple cyclic-dimeric (COOH)2 hydrogen bonding synthons, differing slightly in the grid shape. The Mn-metalled TCPP building blocks afford in a lipophilic environment 2-D coordination polymers by direct Mn-OOC/HOOC association between the tetra-acid metalloporphyrin units, without incorporation of any external bridging auxiliaries. This polymerization is further enforced by interporphyrin O-HO hydrogen bonding within and between the 2-D arrays, yielding a solvent-free 3-D architecture. The latter is related to an isomeric crystalline organization of similar layered Mn-TCPP coordination polymers obtained earlier from hydrophilic crystallization mixtures, wherein intercalated solvent separates the layered polymeric arrays. The non-acidic Mn(Cl)-TOHPP compound yields a chiral 3-D assembly sustained by multiple inter-porphyrin hydrogen bonding. Its formation is promoted by the non-centrosymmetric (axially polarized) shape of this porphyrin unit, as well as by the directional hydrogen bonding interactions, and it involves coordination of an additional axial ligand to the manganese ion. Effects of competing solvation, which interfere with the supramolecular aggregation of the TCPP scaffolds into network arrays, are demonstrated also by structures obtained from solvent mixtures containing dimethylsulfoxide.

Identifiers
urn:nbn:se:ltu:diva-11178 (URN)10.1039/b601889k (DOI)a1530870-06df-11dd-97e0-000ea68e967b (Local ID)a1530870-06df-11dd-97e0-000ea68e967b (Archive number)a1530870-06df-11dd-97e0-000ea68e967b (OAI)
Note
Upprättat; 2006; 20080410 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
George, S., Lipstman, S. & Goldberg, I. (2006). Porphyrin supramolecular solids assembled with the aid of lanthanide ions (ed.). Paper presented at . Crystal Growth & Design, 6(12), 2651-2654
Open this publication in new window or tab >>Porphyrin supramolecular solids assembled with the aid of lanthanide ions
2006 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 6, no 12, p. 2651-2654Article in journal (Refereed) Published
Abstract [en]

Reactions of free-base tetra(4-carboxyphenyl)porphyrin with lanthanide ions as Pr3+, Dy3+, and Nd3+ led to open metal-organic framework solids sustained by polynuclear metal-carboxylate clusters. Their three-dimensional structures are characterized by channel voids accessible to other guest components (e.g., water, small organics). Crystalline solids obtained by the hydrothermal synthesis with Dy3+ and Nd3+ reagents reveal remarkable stability and represent the first example of hybrid porphyrin-lanthanide single framework architectures.

Identifiers
urn:nbn:se:ltu:diva-14631 (URN)10.1021/cg060520r (DOI)e082be50-07b6-11dd-97e0-000ea68e967b (Local ID)e082be50-07b6-11dd-97e0-000ea68e967b (Archive number)e082be50-07b6-11dd-97e0-000ea68e967b (OAI)
Note
Upprättat; 2006; 20080411 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
George, S. (2006). Self-assembly of porphyin arrays by hydrogen bonding and supramolecular isometrism in porphyrin networks (ed.). Paper presented at Israel Crystallographic Association meeting : 29/05/2006. Paper presented at Israel Crystallographic Association meeting : 29/05/2006.
Open this publication in new window or tab >>Self-assembly of porphyin arrays by hydrogen bonding and supramolecular isometrism in porphyrin networks
2006 (English)Conference paper, Oral presentation only (Other academic)
Identifiers
urn:nbn:se:ltu:diva-32676 (URN)73cc6500-053a-11dd-b034-000ea68e967b (Local ID)73cc6500-053a-11dd-b034-000ea68e967b (Archive number)73cc6500-053a-11dd-b034-000ea68e967b (OAI)
Conference
Israel Crystallographic Association meeting : 29/05/2006
Note
Upprättat; 2006; 20080408 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
George, S. & Goldberg, I. (2006). Self-assembly of supramolecular porphyrin arrays by hydrogen bonding: New Structures and Reflections (ed.). Paper presented at . Crystal Growth & Design, 6(3), 755-762
Open this publication in new window or tab >>Self-assembly of supramolecular porphyrin arrays by hydrogen bonding: New Structures and Reflections
2006 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 6, no 3, p. 755-762Article in journal (Refereed) Published
Abstract [en]

This study relates to the self-assembly of the free-base 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP), six-coordinate manganese-5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin with molecules of water or methanol as axial ligands [MnIII(H2O)2-TCPP or MnIII(CH3OH)2-TCPP, respectively], and manganese chloride-5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin [MnIII(Cl)-TOHPP] into multiporphyrin hydrogen-bonding "polymers". In the first case, the porphyrin units hydrogen bond directly to each other through their carboxylic acid functions. The two-dimensional (2D) square-grid polymeric arrays thus formed are sustained by characteristic intermolecular cyclic dimeric (COOH)2 hydrogen-bond synthons between a given porphyrin unit and four other neighboring species along the equatorial directions. They stack tightly one on top of the other in an offset manner along the normal direction, yielding channeled lattice architecture. In an aqueous basic environment insertion of MnIII into the porphyrin core involves deprotonation of one of the carboxylic groups, to balance the charge, and attraction of two water molecules as axial ligands. The MnIII(H2O)2-TCPP units hydrogen bond, however, directly to one another through their carboxylic/carboxylate functions in the equatorial plane in a catemeric (rather than cyclic dimeric) manner. The 2D networks that form in this case are interconnected in the normal direction by additional hydrogen bonds through the axial water ligands, yielding a three-dimensional (3D) hydrogen-bonding architecture. In a methanolic solution of H3PO4, the methanol molecules replace water as axial ligands to the metal ion. The phosphate anions balance the extra positive charge of the trivalent metal, and they act also as effective bridges between adjacent MnIII(CH3OH)2-TCPP moieties by interacting as proton acceptors with the peripheral carboxylic functions of four different porphyrins. This affords open square-grid-type layers with alternating porphyrin and phosphate components. The 2D arrays stack in an offset manner, interconnecting to one another through hydrogen bonds involving the methanol axial ligands. The Mn(Cl)-TOHPP building blocks arrange in a unique tetragonal structure around axes of 4-fold rotation and self-assemble through multiple O-HCl- attractions between neighboring units into a single-framework hydrogen-bonding polymer. The directional asymmetry introduced to them by the Cl-axial ligand, which is amplified by the preferred hydrogen-bonding scheme, induces the formation of a noncentrosymmetric crystal structure. The nanoporous nature of TCPP-based multiporphyrin assemblies and the chirality of the Mn(Cl)-TOHPP structure are highlighted.

Identifiers
urn:nbn:se:ltu:diva-9825 (URN)10.1021/cg050624m (DOI)882e39a0-063f-11dd-97e0-000ea68e967b (Local ID)882e39a0-063f-11dd-97e0-000ea68e967b (Archive number)882e39a0-063f-11dd-97e0-000ea68e967b (OAI)
Note
Upprättat; 2006; 20080409 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved

Search in DiVA

Show all publications