@article{yan_olmstead_maggard_2007, title={Effect of Spin-Ladder Topology on 2D Charge Ordering:  Toward New Spin-Antiferroelectric Transitions}, volume={129}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja0754709}, DOI={10.1021/ja0754709}, abstractNote={The low-temperature structures of M(pyz)V4O10 (M = Co, Zn) in the spin-gapped state have been investigated by single-crystal X-ray diffraction and electronic structure calculations and provide evidence for a new type of spin-antiferroelectric transition for M = Zn. This new type of phase transition involves the onset of charge ordering within spin ladders that can be mediated by the metal-organic chains via a modification of the inter-ladder interactions.}, number={42}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Yan, Bangbo and Olmstead, Marilyn M. and Maggard, Paul A.}, year={2007}, month={Oct}, pages={12646–12647} }
 @article{yan_maggard_2007, title={M(bipyridine)V4O10 (M = Cu, Ag): Hybrid analogues of low-dimensional reduced vanadates}, volume={46}, ISSN={["1520-510X"]}, DOI={10.1021/ic700729q}, abstractNote={New hybrid layered vanadates, M(bpy)V4O10 (I, M = Cu+; II, M = Ag+; bpy = 4,4'-bipyridine), were prepared from hydrothermal reactions at 220-230 degrees C, and their structures were characterized by single-crystal X-ray diffraction [I, P21/c (No. 14), Z = 4, a = 3.6154(3) A, b = 21.217(1) A, c = 20.267(1) A, and beta = 90.028(3) degrees ; II, P (No. 2), Z = 2, a = 3.5731(4) A, b = 10.429(1) A, c = 21.196(2) A, alpha = 89.031(5) degrees , beta = 89.322(5) degrees , and gamma = 85.546(5) degrees ]. The structures of I and II are closely related, though not isostructurally, with both containing partially reduced V4O10- layers that are constructed from zigzag chains of edge-sharing VO5 tetragonal pyramids. Neighboring zigzag chains within a layer condense via shared vertices and alternate between versions containing V4.5+ and V5+ ions, such that two out of four symmetry-unique V atoms are reduced by a half-electron on average. The interlayer spaces contain unusual M(bpy)+ chains formed from the coordination of two bridging bpy ligands to Ag+/Cu+ in a nearly linear fashion and each with a third bond to a single apical O atom of the reduced (V4.5+) VO5 tetragonal pyramids. Both I and II are stable until approximately 350-400 degrees C in O2, at which point the ligands are liberated to yield the purely inorganic MxV4O10 (M = Ag, Cu) solids. The electrical conductivities of both compounds show a temperature dependence that is consistent with Mott's variable-range-hopping model for randomly localized electrons. Magnetic susceptibilities of both I and II can be fitted to a Curie-Weiss expression (theta = -25 and -31 K, respectively; C approximately 0.40 emu.mol-1.K for both) at higher temperatures and one unpaired spin per formula. However, at below approximately 12-18 K, both show evidence for an antiferromagnetic transition that can be fitted well to the Heisenberg linear antiferromagnetic chain model. These results are analyzed with respect to related reduced vanadates and help to provide new structure-property insights for strongly correlated electron systems.}, number={16}, journal={INORGANIC CHEMISTRY}, author={Yan, Bangbo and Maggard, Paul A.}, year={2007}, month={Aug}, pages={6640–6646} }
 @article{yan_maggard_2006, title={Polar Symmetry and Intercalation of New Multilayered Hybrid Molybdates:  [M2(pzc)2(H2O)x][Mo5O16] (M = Co, Ni)}, volume={45}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic060253e}, DOI={10.1021/ic060253e}, abstractNote={The layered molybdate [M2(pzc)2(H2O)x][Mo5O16] (I: M = Ni, x = 5.0; II: M = Co, x = 4.0; pzc = pyrazinecarboxylate) hybrid solids were synthesized via hydrothermal reactions at 160-165 degrees C. The structures were determined by single-crystal X-ray diffraction data for I (Cc, Z = 4; a = 33.217(4) A, b = 5.6416(8) A, c = 13.982(2) A, beta = 99.407(8) degrees , and V = 2585.0(6) A3) and powder X-ray diffraction data for II (C2/c, Z = 4; a = 35.42(6) A, b = 5.697(9) A, c = 14.28(2) A, beta = 114.95(4) degrees , and V = 2614(12) A3). The polar structure of I contains new [Ni2(pzc)2(H2O)5]2+ double layers that form an asymmetric pattern of hydrogen bonds and covalent bonds to stair-stepped [Mo5O16]2- sheets, inducing a net dipole moment in the latter. In II, however, the [Co2(pzc)2(H2O)4]2+ double layers have one less coordinated water and subsequently exhibit a symmetric pattern of covalent and hydrogen bonding to the [Mo5O16]2- sheets, leading to a centrosymmetric structure. Thermogravimetric analyses and powder X-ray diffraction data reveal that I can be dehydrated and rehydrated with from 0 to 6.5 water molecules per formula unit, which is coupled with a corresponding contraction/expansion of the interlayer distances. Also, the dehydrated form of I can be intercalated by approximately 4.3 H2S molecules per formula unit, but the intercalation by pyridine or methanol is limited to less than one molecule per formula unit.}, number={12}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Yan, Bangbo and Maggard, Paul A.}, year={2006}, month={Jun}, pages={4721–4727} }
 @article{yan_luo_dube_sefat_greedan_maggard_2006, title={Spin-Gap Formation and Thermal Structural Studies in Reduced Hybrid Layered Vanadates}, volume={45}, ISSN={0020-1669 1520-510X}, url={http://dx.doi.org/10.1021/ic0604563}, DOI={10.1021/ic0604563}, abstractNote={Reduced layered M(C4H4N2)V4O10 ((I, M = Co; II, M = Ni; III, M = Zn); C4H4N2 = pyrazine, pyz) hybrid solids were synthesized via hydrothermal reactions at 200-230 degrees C, and their structures determined by single-crystal X-ray diffraction (Cmcm, No. 63, Z = 4; a = 14.311(2), 14.2372(4), 14.425(1) A; b = 6.997(1), 6.9008(2), 6.9702(6) A; and c = 11.4990(8), 11.5102(3), 11.479(1) A; for I, II, and III, respectively). All three solids are isostructural and contain V4O102- layers condensed from edge- and corner-shared VO5 square pyramids. A single symmetry-unique V atom is reduced by 1/2 electron (on average) and bonds via its apical oxygen atom to interlayer Mpyz2+ chains. Magnetic susceptibility measurements show a strong temperature dependence and a Curie constant that is consistent with two randomly localized spins per V4O10(2-) formula for III. Further, the unusual discovery of a remarkably well-defined transition to a singlet ground state, as well as formation of a spin gap, is found for III at 22(1) K. The temperature-dependent electrical conductivities show apparent activation energies of 0.36 (I), 0.46 (II), and 0.59 eV (III). During heating cycles in flowing N2, the samples exhibit weight losses corresponding to the removal of predominantly pyrazine, pyrazine fragments, and CO2 via reaction of pyrazine with the vanadate layer. The complete removal of pyrazine without loss of crystallinity is found for well-ground samples of I and III. The SEM images of I and II after heating at 400-500 degrees C show relatively intact crystals, but at 600 degrees C further structural collapse results in the formation of macropores at the surfaces.}, number={13}, journal={Inorganic Chemistry}, publisher={American Chemical Society (ACS)}, author={Yan, Bangbo and Luo, Junhua and Dube, Paul and Sefat, Athena S. and Greedan, John E. and Maggard, Paul A.}, year={2006}, month={Jun}, pages={5109–5118} }
 @article{maggard_yan_luo_2005, title={Pillared hybrid solids with access to coordinatively unsaturated metal sites: An alternative strategy}, volume={44}, ISSN={["1521-3773"]}, DOI={10.1002/anie.200462715}, abstractNote={A layered effect: Replacement of pyrazine (A) with Co- or Ni-coordinated 2-pyrazinecarboxylate (pzc; B) between neutral AgReO4 layers (red and blue polyhedra) yields M(pzc)2(H2O)2AgReO4 (M=Co (shown) or Ni). This novel strategy is aimed at pillared solids with coordinated H2O that can be reversibly removed without causing structural collapse to give coordinatively unsaturated Ni and Co sites.}, number={17}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Maggard, PA and Yan, BB and Luo, JH}, year={2005}, pages={2553–2556} }
 @article{yan_capracotta_maggard_2005, title={Structural origin of chirality and properties of a remarkable helically pillared solid}, volume={44}, ISSN={["1520-510X"]}, DOI={10.1021/ic050794o}, abstractNote={A new helically pillared and chiral solid, Cu(pzc)2AgReO4 (I, pzc = pyrazinecarboxylate), was synthesized from hydrothermal reactions at 95-125 degrees C. The structural origin of its chirality, relative to the achiral M(pzc)2(H2O)2AgReO4 (II, M = Co; III, M = Ni) analogues, arises from significantly tilted pillars and hydrogen bonds to the AgReO4 layers. The new pillared structure exhibits second harmonic generation activity, CO2 absorption, thermal stability to approximately 250 degrees C, and Curie-Weiss magnetism expected for isolated Cu2+.}, number={19}, journal={INORGANIC CHEMISTRY}, author={Yan, BB and Capracotta, MD and Maggard, PA}, year={2005}, month={Sep}, pages={6509–6511} }
 @article{lin_yan_boyle_maggard_2006, title={Synthesis and Properties of Pyrazine-Pillared Ag3Mo2O4F7 and AgReO4 Layered Phases}, volume={179}, ISSN={["1095-726X"]}, DOI={10.1016/j.jssc.2005.10.037}, abstractNote={The new pyrazine-pillared solids, AgReO4(C4H4N2) (I) and Ag3Mo2O4F7(C4H4N2)3 (C4H4N2=pyrazine, pyz) (II), were synthesized by hydrothermal methods at 150 °C and characterized using single crystal X-ray diffraction (I—P21/c, No. 14, Z=4, a=7.2238(6) Å, b=7.4940(7) Å, c=15.451(1) Å, β=92.296(4)°; II—P2/n, No. 13, Z=2, a=7.6465(9) Å, b=7.1888(5) Å, c=19.142(2) Å, β=100.284(8)°), thermogravimetric analysis, UV-Vis diffuse reflectance, and photoluminescence measurements. Individual Ag(pyz) chains in I are bonded to three perrhenate ReO4– tetrahedra per layer, while each layer in II contains sets of three edge-shared Ag(pyz) chains (π–π stacked) that are edge-shared to four Mo2O4F73– dimers. A relatively small interlayer spacing results from the short length of the pyrazine pillars, and which can be removed at just slightly above their preparation temperature, at >150–175 °C, to produce crystalline AgReO4 for I, and Ag2MoO4 and an unidentified product for II. Both pillared solids exhibit strong orange-yellow photoemission, at 575 nm for I and 560 nm for II, arising from electronic excitations across (charge transfer) band gaps of 2.91 and 2.76 eV in each, respectively. Their structures and properties are analyzed with respect to parent ‘organic free’ silver perrhenate and molybdate solids which manifest similar photoemissions, as well as to the calculated electronic band structures.}, number={1}, journal={Journal of Solid State Chemistry}, author={Lin, H. and Yan, B. and Boyle, P.D. and Maggard, P}, year={2006}, pages={217–225} }