Gregory J. Grant

University of Tennessee at Chattanooga, Chattanooga, Tennessee, United States

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Publications (74)102.03 Total impact

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    ABSTRACT: We report the synthesis and characterization for several gold(III) complexes involving a series of cyclometallating ligands. These cyclometallating ligands (CˆN) are: 2-phenylpyridine (ppy), 2-(p-tolyl)pyridine (tpy), 2-(2′-benzothienyl)pyridine (btp) and 7,8-benzoquinoline (bzq). With the assistance of TGA data, we have developed solventless reactions to prepare the neutral cyclometallated Au(III) dichloro complexes. Reaction of these with the crown trithioether [9]aneS3 (1,4,7-trithiacyclononane), followed by metathesis with NH4PF6, yields the heteroleptic complexes [Au([9]aneS3)(CˆN)](PF6)2. The X-ray structures of the gold(III) [9]aneS3 complexes display axial Au–S interactions formed by the endodentate conformation of the thiacrown, resulting in elongated square pyramidal geometries. The Au–S axial distance correlates with the electron-donating properties of the CˆN ligand with the better donating btp showing the longest distance (2.855(1) Å) while the ppy shows the shortest (2.818(1) Å). The coordinated [9]aneS3 ligand shows fluxional behavior by its NMR spectroscopy, resulting in a single 13C NMR resonance despite the asymmetric coordination environment of the cyclometallating ligand. Electrochemical studies of the [9]aneS3 complexes reveal irreversible one-electron reductions which are assigned as a Au(III)/Au(II) couple. The ease of reduction correlates with the axial Au–S distances with the btp being the easiest to reduce and the ppy the most difficult. In addition, we report the crystal structures for three intermediate complexes: [Au(H-tpy)Cl3], [Au(H-btp)Cl3], and [Au(btp)Cl2]. The [Au(H-btp)Cl3] complex shows an interesting Au–S axial interaction at 3.139(2) Å which alters the physicochemical properties of the complex.
    Journal of Organometallic Chemistry 01/2014; 755:47–57. · 2.00 Impact Factor
  • Gregory J. Grant
    ChemInform 10/2012; 43(42).
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    ABSTRACT: doi: 10.1021/om3006382
    Organometallics 08/2012; 31(18):6505-6513. · 4.15 Impact Factor
  • Gregory J Grant
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    ABSTRACT: Platinum(II) and palladium(II) complexes of the trithiacrown [9]aneS(3) containing a range of Group 15 donors are reviewed. These complexes have the general formula [M([9]aneS(3))(L(2))](n+) where L represents at least one Group 15 donor. Complexes involving pnictogens, with the exception of bismuth, are observed. The complexes generally have an elongated square pyramidal geometry with a long distance interaction to the third sulphur of the [9]aneS(3) which forms the apex of the square pyramid. This axial metal-sulphur distance is quite sensitive to the donor properties of L. Poorer donors such as Sb and As ligands show short axial distances whereas the better N donor ligands show longer distances. Pt(II) complexes of the formula [Pt([9]aneS(3))(EPh(3))(2)](2+) (E = P, As, Sb) show a considerable distortion towards a trigonal bipyramidal geometry due to intramolecular π-π interactions. Over seventy of these types of complexes have been crystallographically characterized and are discussed in this article. Other unique features of the complexes, including NMR spectroscopy, redox chemistry, and electronic spectroscopy, are also discussed.
    Dalton Transactions 06/2012; 41(29):8745-61. · 4.10 Impact Factor
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    ABSTRACT: We wish to report the synthesis, crystal structures, spectroscopic and electrochemical properties of several new Pt(II) heteroleptic complexes containing the thiacrown, 9S3 (1,4,7-trithiacyclononane) with a series of substituted phenanthroline ligands and related diimine systems. These five ligands are 5,6-dimethyl-1,10-phenanthroline(5,6-Me2-phen), 4,7-dimethyl-1,10-phenanthroline(4,7-Me2-phen), 4,7-diphenyl-1,10-phenanthroline(4,7-Ph2-phen), 2,2′-bipyrimidine(bpm), and pyrazino[2,3-f]quinoxaline or 1,4,5,8-tetraazaphenanthrene(tap). All complexes have the general formula [Pt(9S3)(N2)](PF6)2 (N2=diimine ligand) and form similar structures in which the Pt(II) center is surrounded by a cis arrangement of the two N donors from the diimine chelate and two sulfur atoms from the 9S3 ligand. The third 9S3 sulfur in each structure forms a longer interaction with the platinum resulting in an elongated square pyramidal structure, and this distance is sensitive to the identity of the diimine ligand. In addition, we report the synthesis, structural, electrochemical, and spectroscopic properties of related Pd(II) 9S3 complex with tap. The 195Pt NMR chemical shifts for the six Pt(II) complexes show a value near −3290ppm, consistent with a cis-PtS2N2 coordination sphere although more electron-withdrawing ligands such as tap show resonances shifted by almost 100ppm downfield. The physicochemical properties of the complexes generally follow the electron-donating or withdrawing properties of the phenanthroline substituents.
    Polyhedron 01/2012; · 2.05 Impact Factor
  • Source
    John P Lee, Gregory J Grant, Bruce C Noll
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    ABSTRACT: The homoleptic thio-ether title complex, [Ni(C(6)H(12)S(3))(2)](BF(4))(2)·2CH(3)NO(2), shows the expeced hexa-kis-(thio-ether) octa-hedral environment around the Ni(II) atom. It crystallized as two crystallographically independent complex cations, [Ni(9S3)(2)](2+) (9S3 = 1,4,7-trithia-cyclo-nona-ne), within the unit cell where each Ni(II) lies on an inversion center. In addition to the complex cations, there are two crystallographically independent BF(4) (-) anions present to balance the charge, and each shows disorder along a pseudo-C(3) axis with ratios of 0.53 (2):0.47 (2) and 0.55 (2):0.45 (2). Two nitro-methane solvent mol-ecules per complex cation are also present in the unit cell.
    Acta Crystallographica Section E Structure Reports Online 10/2011; 67(Pt 10):m1417-8. · 0.35 Impact Factor
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    ABSTRACT: AbstractWe wish to report the crystal structure for a solid-state solution, {[Pt(9S3)Cl2]2[Pt(9S3)2]}Cl2·4H2O (1), which contains two different complexes of Pt(II) with the trithiacrown 9S3 (1,4,7-trithiacyclononane). One complex [Pt(9S3)Cl2] is neutral and contains a Pt(II) center with a single 9S3 ligand and two coordinated chloro ligands. The second Pt(II) complex is a dication and contains two coordinated 9S3 ligands and two non-coordinating chloride anions. There are two crystallographically equivalent [Pt(9S3)Cl2] complexes present for every single [Pt(9S3)2]2+ cation. Four water solvent molecules are also present. In the neutral complex ([Pt(9S3)Cl2], the Pt(II) center is surrounded by a cis-[S2Cl2+S1] ligand environment formed by the two chloro ligands and two of the three sulfur atoms from the 9S3 ligand. These two sulfurs are positioned 2.225(2) and 2.242(2)Å from the Pt(II), but the third sulfur shows a long distance interaction at 3.311(2)Å to form an elongated square pyramidal structure. This axial Pt–S distance is the longest observed in 57 crystal structures of Pt(II) 9S3 complexes. The cation [Pt(9S3)2]2+ displays two centrosymmetrically coordinated 9S3 ligands forming a [S4+S2] environment with an elongated octahedral shape. In the dication, the two equatorial Pt–S distances are 2.297(2) and 2.306(2)Å with the axial sulfur at 3.065(2)Å. The most interesting intermolecular aspects of the structure are hydrogen bonding interactions between two of the water molecules and two chloride counter-ions, resulting in a nearly square O2Cl2 ring. This ring shares an edge with a six-membered ring formed by four waters and two chlorides which are hydrogen bonded. The hydrogen bonding interactions, which result from the presence of water in the crystal, appear to be an important component in stabilizing the lattice for the unusual solid-state solution structure. Crystal Data for (1): P2 1 /n, a=7.8327(10)Å, b=25.152(4)Å, c=12.382(2)Å, V=2314.3(6)Å3, Z=2. We also report an improved synthetic procedure for the preparation of two thiacrown complexes [Pt(9S3)Cl2] and [Pt(10S3)Cl2], which are commonly used as precursors for other heteroleptic thioether complexes. The new syntheses proceed at room temperature without the need for long reflux times and produce large crystals which are easily isolable without filtration. The simplicity of these new preparations results in improved yields over previously employed methods. Graphical AbstractThe title complex crystallizes to form a solid-state solution of two different Pt(II) thiacrown complexes, [Pt(9S3)Cl2] and [Pt(9S3)]2+. KeywordsCrown thioethers–Platinum complexes–Solid-state solutions–1,4,7-trithiacyclononane–Hydrogen bonding
    Journal of Chemical Crystallography 01/2011; 41(6):847-853. · 0.51 Impact Factor
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    ABSTRACT: We wish to report the synthesis of the Ru(II) crown thioether complex, (1,4,7,10,13-pentathiacyclopentadecane)chlororuthenium(II) hexafluorophosphate, [Ru([15]aneS5)Cl](PF6), and a study of its properties utilizing single crystal X-ray diffraction, electronic spectroscopy, NMR spectroscopy, density functional theory calculations and cyclic voltammetry. The crystal structure shows a single [15]aneS5 macrocycle and a chloro ligand coordinated in a distorted octahedral fashion around the ruthenium(II) center. A significant shortening (0.15 Å) of the trans Ru–S bond length occurs in this complex compared to the related PPh3 complex (2.4458(10) to 2.283(1) Å) due to the differences in the trans influence of the two ligands. 13C NMR spectroscopy demonstrates that the structure of [Ru([15]aneS5)Cl]+ is retained in solution. As expected for a Ru(II) complex, the electronic absorption spectrum shows two d–d transitions at 402 and 331 nm. These are red-shifted compared to hexakis(thioether)ruthenium(II) complexes and consistent with the weaker ligand field effect of the chloro ligand. The electrochemical behavior of the complex in acetonitrile shows a single one-electron reversible oxidation–reduction at +0.722 V versus Fc/Fc+ which is assigned as the Ru(II)/Ru(III) couple. DFT calculations for [Ru([15]aneS5)Cl]+ show a HOMO with orbital contributions from a t2g type orbital of the Ru ion, a π component from a p orbital of the axial S atom of [15]aneS5, and a p orbital of the chloro ligand while the LUMO consists of orbital contributions of dx2-y2dx2-y2 orbital of the Ru center and p orbitals of the four equatorial S donors.
    Inorganica Chimica Acta 12/2010; 364(1):55-60. · 1.69 Impact Factor
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    ABSTRACT: We report that our previously published molecular square, [{Pt([9]aneS3)(bipy)}4](OTf)8, although quite stable in nitromethane, slowly establishes an equilibrium with another coordination polymer, most likely a triangle, in acetonitrile. Multinuclear measurements on the square precursor complex, [Pt([9]aneS3)Cl2], show acetonitrile coordination upon dechlorination in that solvent, and acetonitrile coordination is additionally confirmed by the solid-state structure of [Pt([9]aneS3)(MeCN)2]2+. We form the complex through the reaction of [Pt([9]aneS3)Cl2] with excess AgPF6 in refluxing MeCN to produce a solid-state solution containing two complex cations with exclusive hexafluorophosphate counterions. Besides [Pt([9]aneS3)(MeCN)2]2+, a second cation is obtained, [Pt([9]aneS3)2]2+, which shows disorder between a double endo and a rare double exo conformation for the two [9]aneS3 ligands. We also report the structures of two Rh(III) thiacrown complexes, cis-[Rh([12]aneS4)Cl2](PF6), which involves cis chloro ligands and an asymmetric binding of the two equatorial sulphur donors, as well as trans-[Rh([16]aneS4)(H2O)(Cl)](OTf)2 with adjacent rather than alternating chair and twist-boat conformations. Lastly, the crystal structure of [{Pd([9]aneS3)(Cl)}2(pyrazine)](OTf)2 displays a pyrazine ligand bridging two [Pd([9]aneS3)Cl]+ moieties with cis stereochemistry of the two chloro ligands. Distortion of the pyrazine ligand is observed, which alleviates strain from bridging the two Pd centres. The extended structure of the complex consists of chains of dimers running parallel to the b-axis of the crystal.
    Supramolecular Chemistry 02/2010; 22(2):109-121. · 1.55 Impact Factor
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    ABSTRACT: The complex [Pt(9S3)(SbPh3)(Ph)](PF6) forms directly from [Pt(9S3)(SbPh3)2](PF6)2 during the room temperature crystallization of the latter in nitromethane. The crystal structure shows a five-coordinate Pt(II) center containing the tridentate thiacrown ligand, a Sb donor from the triphenylstibine ligand, and a σ-coordinating phenyl group. The phenyl group forms via Sb–C bond cleavage from one of the SbPh3 ligands in the bis complex.
    Journal of Organometallic Chemistry - J ORGANOMET CHEM. 01/2010; 695(4):634-636.
  • Hitesh Vikram Vashi, Gregory Grant
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    ABSTRACT: Our group is focused on creating the metal complexes that will self-assemble into molecular cubes, squares, and hexagons. These complexes have a wide range of applications in the modern world, including encapsulating gases and ions, forming efficient conductors for micro and nano electronics, and tumor therapy. In our experiments, we will use the starting complex [Rh(9S3)Cl3] (9S3 = 1, 4, 7-trithiacyclononane) to form a molecular cube, [Rh(12S4)Cl2](PF6) (12S4 = 1, 4, 7, 10-tetrathiacyclododecane) to form a molecular square, and [Rh(16S4)Cl2](PF6) (16S4 = 1, 5, 9, 13-tetrathiacylcohexadecane) to form a molecular hexagon. Dechlorination of these complexes has proven difficult using reactions with AgNO3 and AgPF6. A dibromo analog, [Rh(12S4)Br2](Br), has been prepared and characterized. We have attempted to debrominate the complex as an alternative to the silver dechlorination procedures. By manipulating geometry, bond angles, and favorable interactions, one can feasibly create a supramolecular structure. Also, octahedral complexes of rhodium(III) complexes containing the oxa-thioethers 18S4O2 (1, 10-dioxa-4, 7, 13, 16-tetrathiacyclooctadecane) and 9S2O (1-oxa-4, 7-dithiacyclononane) show full coordination by all oxygen and sulfur donors.
    61st American Chemical Society Southeast Regional Meeting; 10/2009
  • Gregory J. Grant, Rishi D. Naik, Desiree A. Benefield
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    ABSTRACT: Our group has been interested in the preparation and properties of heteroleptic Pt(II) thiacrown complexes with a variety of ancillary ligands. The complexes have the general formula [Pt(9S3)L]2+ where 9S3 is the trithiacrown 1,4,7-trithiacyclononane. We have used 4,4'-bipyridine as a linear linker between four [Pt(9S3)]2+ corners to form a molecular square which has been characterized by single crystal X-ray diffraction, multinuclear NMR, and other methods. We report new evidence for an equilibrium in acetonitrile between the square and the related triangle. In addition, we will describe a series of complexes with Group 15 donors of the form [Pt(9S3)(L)](PF6)2 (L = 2 x PPh3, AsPh3, or SbPh3). The X-ray structures of each complex indicate an axial M-S interaction formed by the endodentate conformation of the 9S3 ligand. The axial M-S distance is highly dependent upon the ancillary donor set. The axial M-S distance shortens with the identity of the Group 15 donor ligand according to the trend, Sb bis pnictogen complexes, [Pt(9S3)(EPh3)2](PF6)2, form unusual five-coordinate distorted trigonal bipyramids in contrast to the pseudo-five coordinate, elongated square pyramidal structures typically observed in Pt(II) complexes of 9S3. The distortion arises from intramolecular π-π interactions between the phenyl rings on different two triphenyl ligands.
    61st American Chemical Society Southeast Regional Meeting; 10/2009
  • Natalie Nicole Talbott, Gregory Grant
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    ABSTRACT: We are interested in exploring Pt(II) complexes containing substituted phenanthroline ligands since they simulate guanine binding by the chemotherapeutic agent cis-platin. These complexes have the general formula [Pt(9S3)(L)](PF6)2where 9S3 is the crown thioether 1,4,7-trithiacyclononane and L represents a bidentate phenanthroline ligand. We have prepared complexes involving a series of these ligands including 5,6-dimethyl-1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, 5-nitro-1,10-phenanthroline, tap (pyrazino[2,3-f]quinoxaline) and bpm (2,2'-bipyrimidine). We have attempted to bind additional bidentate ligands which contain two chelating sulfur donors (o-BMXMe) or two chelating selenium donors (o-BSEXMe) to Pt(II) and Pd(II) 9S3 moieties.
    61st American Chemical Society Southeast Regional Meeting; 10/2009
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    ABSTRACT: We report the synthesis and full characterization for a series of thiacrown complexes of Pt(II) incorporating the fluxional trithiacrown ligand 1,4,7-trithiacyclononane ([9]aneS3) and several group 15 donors ligands. Reaction of [Pt([9]aneS3)Cl2] with a full stoichiometric equivalent of the group 15 donor (L = 2 x AsPh3, SbPh3 or 1,2-bis(diphenylarsenio) ethane (dpae) followed by metathesis with NH4PF6 yields [Pt([9]aneS3)L](PF6)2. We also report the analogous Pd(II) complex with dpae. Similar reactions of the starting Pt complex with one equivalent of XPh3 (X = As or Sb) result in complexes of the formula [Pt([9]aneS3)(XPh3)(Cl)](PF6). All six new complexes have been fully characterized by multinuclear NMR, IR, and UV-Vis spectroscopies in addition to elemental analysis and single crystal structural determinations. The X-ray structures of each complex indicate an axial M-S interaction formed by the endodentate conformation of the [9]aneS3 ligand. The axial M-S distance is highly dependent upon the ancillary donor set. The axial M-S distance shortens with the identity of the group 15 donor ligand according to the trend, Sb < As < P, due to their increasingly poorer donor qualities. The two bis pnictogen complexes, [Pt([9]aneS3)(AsPh3)2](PF6)2 and [Pt([9]aneS3)(SbPh3)2](PF6)2 form unusual five-coordinate distorted trigonal bipyramids in contrast to the pseudo-five coordinate, elongated square pyramidal structures typically observed in Pt(II) complexes of [9]aneS3. The distortion arises from intramolecular pi-pi interactions between the phenyl rings on the two different triphenyl ligands. Chemical shifts in the 195Pt NMR also show similar periodic relationships which trend progressively upfield as the donor atom becomes larger. As expected, the coordinated [9]aneS3 ligand shows fluxional behavior in its NMR spectra, resulting in a single 13C NMR resonance, despite the asymmetric coordination environment found in both chloro complexes. The line width for the carbon NMR resonance as well as for the 195Pt NMR peak is highly sensitive to the nature of the group 15 donor, with poorer donors such as SbPh3 showing significant line broadening. Measurements from the electronic spectra support that the ligand field strength of the pnictogen donor decreases with its increasing size.
    Dalton Transactions 10/2009; · 4.10 Impact Factor
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    ABSTRACT: The two macrocyclic hexathioethers, 1,4,7,12,15,18-hexathiacyclodocosane (22S6) and 1,4,7,11,14,17-hexathiacycloeicosane (20S6) have been examined with respect to their complexation behavior towards a variety of transition metals ions. In all of these complexes, the two ligands generate relatively strong ligand field, but their field strengths fall between the smaller ring and stronger field hexathioether ligands (such as 18S6) and larger ring and weaker field ligands, such as 24S6. The stability of the complexes towards hydrolysis parallels their reduced field strengths with first row transition metal complexes of both ligands showing enhanced sensitivity to solvolysis reactions compared to the analogous 18S6 complexes. In general, the electrochemical behavior of the hexathioether complexes shows metal centered oxidations which occur at higher potentials than those complexes involving trithioethers. We suggest that the hexathioether ligand is less able to expand and contract during the reduction and oxidation of the metal center. The complex [Pd(22S6)]2+ does not display the unusual spectroscopic and electrochemical properties observed in the analogous 18S6 complex.
    Journal of Heterocyclic Chemistry 03/2009; 38(6):1281 - 1289. · 1.22 Impact Factor
  • Hitesh Vikram Vashi, Gregory Grant
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    ABSTRACT: Our group is focused on the preparation of metal thiacrown complexes with Co(III) and Rh(III) that can be used as building blocks to self-assemble into molecular cubes and squares, respectively. Supramolecular complexes such these have important current applications including the encapsulation of gases and anions as well as the formation of efficient conductors for micro and nanoelectronics. The thioether 9S3 (1, 4, 7, trithiacyclononane) is used as the capping ligand for the cobalt complexes and the thioether 12S4 (1, 4, 7, 10 tetrathiacyclododecane) is similarly used for the rhodium complexes. The starting Na3[Co(NO2)6] complex is converted through a series of reactions to form [Co(9S3)(H2O)3](NO3)3. We have then attempted to use this complex in the preparation of a molecular cube. With the [Rh(12S4)Cl2](PF6) complex, full dechlorination is required prior to the self-assembly process. Several synthetic routes for dechlorination of this complex will be discussed. Also, the dibromo analog of the [Rh(12S4)Cl2](PF6) complex, [Rh(12S4)Br2]Br, was prepared and characterized.
    60th American Chemical Society Southeast Regional Meeting; 11/2008
  • Marko Bajic, Gregory J. Grant
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    ABSTRACT: Self assembly, under controlled conditions, is the combination of various components into an organized shape. For our research we use the geometry of [Ru(12S4)(dmso)Cl]PF6, (12S4 = 1,4,7,10-tetrathiacyclododecane), to form a square and [Ru(9S3)(dmso)Cl2], (9S3 = 1,4,7-trithiacyclcononane), to form a cube as the final products. To achieve the final self assembled products the starting complexes need to be dechlorinated. Herein we report the results of the dechlorination of both complexes through the use of TlPF6. We also report the results of the dechlorination of [Ru(9S3)(dmso)Cl2] through the use of AgOTf, (OTf = triflate), and AgPF6. We also did research on a variety of ligands including pyrazine, 4,4'-bipyridine, and 1,2-bis(4-pyridyl)ethane that could be used to connect the ruthenium corners of the final self-assembled complex. Our results show that: the use of TlPF6 to dechlorinate the starting ruthenium complexes did not work, AgOTf was able to dechlorinate the starting [Ru(9S3)(dmso)Cl2] complex while AgPF6 was not, and that pyrazine and 4,4'-bipyridine are able to link two ruthenium corners together.
    60th American Chemical Society Southeast Regional Meeting; 11/2008
  • Desiree A. Biggers, Gregory J. Grant
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    ABSTRACT: Our group is interested in the periodic trends of Group 15 donor ligands in Pt(II) thiacrown complexes and examining the effects that these ligands have on complexation behavior. We report the synthesis and full characterization for a series of Pt(II) complexes incorporating the trithiacrown ligand 1,4,7-trithiacyclononane (9S3) and several Group 15 donor ligands. Reaction of [Pt(9S3)Cl2] with a full stoichiometric equivalent of the Group 15 ligand (L = 2 x AsPh3, SbPh3 or 1,2-bis(diphenylarsenio)ethane (dpae)) followed by metathesis with NH4PF6 yields [Pt(9S3)L](PF6)2. Similar syntheses with a single equivalent of XPh3 (X = As or Sb) result in compounds of the formula [Pt(9S3)(XPh3)(Cl)](PF6) which show different NMR characteristics. All new complexes have been fully characterized by multinuclear NMR, IR, and UV-Vis spectroscopies in addition to elemental analysis, cyclic voltammetry, and single crystal structural determinations. The X-ray structures of every complex show an axial Pt-S interaction formed by the endodentate conformation of the 9S3 ligand. This platinum-sulfur distance is highly dependent upon the ancillary donor set and follows a periodic trend for the Group 15 donors. The structure of the complex [Pt(9S3)(AsPh3)2](PF6)2 shows a rare five-coordinate trigonal bipyramid as opposed to the pseudo-five coordinate elongated square pyramidal structures typically observed in Pt(II) 9S3 complexes. Trends and distinctions among the phosphorus, arsenic, and antimony donors in the platinum thiacrown complexes will be discussed.
    60th American Chemical Society Southeast Regional Meeting; 11/2008
  • Gregory J. Grant, Maikel E. Botros, Jared S. Hassler
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    ABSTRACT: Our group has been interested in developing correlations between heavy metal NMR chemical shifts (113Cd, 199Hg) and ligand coordination environments. We wish to report a series of homoleptic Hg(II) and Cd(II) complexes involving mixed donor macrocyclic ligands. These ligands include the mixed oxa thiacrowns 9SO (1-oxa-4,7-dithiacyclononane) and 18S4O2 (1,10-dioxa-4,7,13, 16-hexathiacyclooctadecane) as well as the aza thiacrown 9N2S (1-thia-4,7-diazacyclononane). All Cd(II) complexes are six-coordinate, with coordination through all donor atoms in the macrocyclic ligand. In contrast, the oxophobicity of mercury(II) is seen in the complexation behavior of the two S,O macrocycles. The oxygen donors are not coordinated to the Hg center, but rather are oriented in an exodentate fashion. Changes in NMR chemical shifts for the heavy metal nuclei are consistent with the nature of the ligand donor set. In examining the coordination behavior of the oxa azacrown 18N2O4 (1,10-diaza-4,7,13,16-tetraoxacyclooctadecane) towards Cd(II), we have discovered that the complex reacts with atmospheric carbon dioxide. Its unusual crystal structure shows three [Cd(18N2O4)]2+ complexes bridged in 3 fashion by a single carbonate ion, formed from CO2.
    60th American Chemical Society Southeast Regional Meeting; 11/2008
  • Rishi Dilipkumar Naik, Gregory Grant
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    ABSTRACT: One main focus in our group is the preparation of transition metal complexes that will self-assemble into molecular squares. We are interested in using thioether complexes of Pt(II) and Pd(II) in the preparation of these squares via metal-templated self-assembly. These squares have important applications in modern chemistry due to their wide usage throughout supramolecular chemistry, molecular recognition, self-assembly, and host-guest chemistry. In order to control bond angles and geometry, the polydentate chelating ligand 9S3 (1,4,7 trithiacyclononane) was used with both metal corners, which are linked with the ligand 4,4'-bipyridine to form the square. We also wish to report the synthesis and characterization of the complex used as corner units, [Pt(9S3)(CH3CN)2]2+, including its single-crystal X-ray structure. Moreover, we are interested in looking at the dynamic effects of solvent on our complex. In addition, we expanded our research to include a variety of linker ligands, such as pyrazine, 1,2-(4-pyridyl) ethane, pyrazino-[2,3-f] quinoxaline, and 2,7-diazapyrene, in attempts to prepare molecular squares with varying edge lengths.
    60th American Chemical Society Southeast Regional Meeting; 11/2008

Publication Stats

99 Citations
102.03 Total Impact Points

Institutions

  • 1989–2014
    • University of Tennessee at Chattanooga
      • Department of Chemistry
      Chattanooga, Tennessee, United States
  • 2008
    • Saint Catherine University
      • Department of Chemistry
      Saint Paul, MN, United States
    • Clemson University
      • Department of Chemistry
      Clemson, SC, United States
  • 2006
    • International Union of Toxicology
      Reston, Virginia, United States
  • 1994–1996
    • University of Alabama in Huntsville
      • Department of Chemistry
      Huntsville, AL, United States