Korey P. Carter

A series of Ln-p-chlorobenzoic acid–terpyridine complexes: lanthanide contraction effects, supramolecular interactions and luminescent behavior

Fifteen new lanthanide p-chlorobenzoic acid complexes, [PrL3(terpy)(H2O)]2 (1), [LnL3(terpy)(H2O)]2 (Ln = Nd (2), Sm (3), and Eu (4)), and [LnL3(terpy)(H2O)] (Ln = Sm (3′), Eu (4′), Gd (5), Tb (6), Dy (7), Ho (8), Er (9), Tm (10), Yb (11), Lu (12), and Y (13); HL: p-chlorobenzoic acid; terpy: 2,2′:6′,2′′-terpyridine), have been synthesized hydrothermally at varying temperatures and structurally characterized by single crystal and powder X-ray diffraction. The series is comprised of binuclear molecular units (Pr–Eu) that give way to mononuclear molecular complexes (Sm–Y) as the lanthanide contraction takes effect. All fifteen complexes feature a tridentate terpyridine ligand, p-chlorobenzoic acid ligands exhibiting multiple binding modes, bidentate, bridging bidentate, and monodentate, and a bound water molecule. Binuclear complexes 1–4 are stitched together via intermolecular interactions: aromatic–aromatic interactions for 1, halogen⋯halogen interactions for 2–4, to form 1D chains. Mononuclear complexes 3′, 4′, and 5–13 utilize supramolecular hydrogen and halogen bonding to form 2D sheets. Visible and near-IR solid state luminescence studies were performed on complexes 2, 3, 3′, 4, 4′, 6, 7 and 11 and the characteristic visible luminescence of Sm(III), Eu(III), Tb(III), and Dy(III) was exhibited. The near-IR spectra of the Nd(III) and Yb(III) complexes exhibit weak characteristic luminescence, showing that terpy can act as a sensitizing chromophore in these systems.

Combining coordination and supramolecular chemistry to explore uranyl assembly in the solid state

The syntheses and crystal structures of twelve new compounds containing the UO22+ cation, a bromo-substituted benzoic acid linker (m-bromo-, p-bromo, or 3,5-dibromobenzoic acid) and a chelating N-donor (1,10-phenanthroline, 2,2′:6′,2′′-terpyridine, or 4′-chloro-2,2′:6′,2′′-terpyridine) are reported. Single crystal X-ray diffraction analyses of these materials allowed for the exploration of the structural relationship between the benzoic acids and the chelating N-donor, as well as the influence of pH on uranyl speciation. At an unadjusted pH (∼3) a mix of uranyl monomers and dimers are observed whereas at higher pH (5–6) uranyl dimers are usually produced with monomers and tetramers also observed. A systematic study of the supramolecular interactions present in these materials was executed by varying the bromine position on the benzoic acid groups along with substituents on the chelating N-donor. Assembly via halogen and hydrogen bonding interactions as well as π–π interactions, including four instances of uranyl oxo-functionalization via halogen bonding, was observed depending on the experimental conditions utilized.

Supramolecular Assembly of Molecular Rare-Earth–3,5-Dichlorobenzoic Acid–2,2′:6′,2″-Terpyridine Materials: Structural Systematics, Luminescence Properties, and Magnetic Behavior

The syntheses and crystal structures of 16 new rare-earth (RE = La(3+)-Y(3+))-3,5-dichlorobenzoic acid-terpyridine molecular materials characterized via single-crystal and powder X-ray diffraction are reported. These 16 complexes consist of four unique structure types ranging from molecular dimers (La(3+) and Ce(3+)) to tetramers (Pr(3+)-Y(3+)) as one moves across the RE(3+) series. This structural evolution is accompanied by subsequent changes in modes of supramolecular assembly (halogen bonding, halogen-π, halogen-halogen, and π-π interactions). Solid-state visible and near-infrared lifetime measurements were performed on complexes 6 (Sm(3+)), 7 (Eu(3+)), 9 (Tb(3+)), 10 (Dy(3+)), 11 (Ho(3+)), 12 (Er(3+)), and 14 (Yb(3+)), and characteristic emission was observed for all complexes except 11. Lifetime data for 11, 12, and 14 suggest sensitization by the terpy antenna does occur in near-infrared systems, although not as efficiently as in the visible region. Additionally, direct current magnetic susceptibility measurements were taken for complexes 10 (Dy(3+)) and 12 (Er(3+)) and showed dominant ferromagnetic behavior.

Harnessing uranyl oxo atoms via halogen bonding interactions in molecular uranyl materials featuring 2,5-diiodobenzoic acid and N-donor capping ligands

The syntheses and crystal structures of five new compounds containing the UO22+ cation, 2,5-diiodobenzoic acid, and a chelating N-donor (2,2′-bipyridine (bipy) (1), 1,10-phenanthroline (phen) (2 and 3), 2,2′:6′,2′′-terpyridine (terpy) (4), or 4′-chloro-2,2′:6′,2′′-terpyridine (Cl-terpy) (5)) are described and the spectroscopic properties (both vibrational and luminescent) and stretching and interaction force constants of complexes 2, 4, and 5 are reported. Single crystal X-ray diffraction analysis of these materials shows that variation of the chelating N-donor with the same benzoic acid featuring multiple, polarizable halogens at the periphery allows for the systematic accessing of uranyl oxo atoms for non-covalent assembly, which is notable as these atoms are generally terminal. Spectroscopic characterization of complexes 2, 4, and 5 indicate that oxo atom participation in halogen bonding interactions may complement the effects of the electron donating ability of the capping ligand on corresponding uranyl luminescence and vibrational spectra, each contributing to the observed bathochromic shifts.

RE-p-halobenzoic acid–terpyridine complexes, Part II: structural diversity, supramolecular assembly, and luminescence properties in a series of p-bromobenzoic acid rare-earth hybrid materials

Twenty-four new rare-earth p-bromobenzoic acid complexes, [RE(L1)3(L2)(H2O)]2 (RE = La3+ (1), Ce3+ (2), Pr3+ (3), Nd3+ (4)), [RE(L1)3(L2)(H2O)]2 (RE = La3+ (1′), Ce3+ (2′), Pr3+ (3′), Nd3+ (4′)), [RE(L1)3(L2)]2·H2O (RE = Sm3+ (5), Eu3+ (6), Gd3+ (7), Tb3+ (8)), RE(L1)3(L2)(H2O) (RE = Gd3+ (7′), Tb3+ (8′), Dy3+ (9), Ho3+ (10), Er3+ (11), Tm3+ (12), Yb3+ (13), Lu3+ (14), Y3+ (15)), and RE2(L1)4(L2)2(Ox) (RE = Tm3+ (12′), Yb3+ (13′) Lu3+ (14′)); L1: p-bromobenzoic acid; L2: 2,2′:6′,2′′-terpyridine; Ox: oxalic acid, have been hydrothermally synthesized and structurally characterized by single crystal and powder X-ray diffraction. The series includes binuclear molecular complexes [(La3+–Nd3+), (La′3+–Nd′3+), (Sm3+–Tb3+)], which transition to pseudo-dimeric units (Gd3+–Y3+) as a result of the lanthanide contraction. The range of structures is completed by distinct oxalate-bridged binuclear complexes (Tm3+–Lu3+), formed via in situ synthesis, that appear only with the smallest lanthanides and only from higher temperature syntheses. There are subtle differences in coordination environments between the five structure types as a result of the lanthanide contraction, despite all complexes in this study containing binuclear units. All twenty-four complexes feature halogen- and π-based supramolecular interactions which assemble the molecular complexes into one, two, and three dimensions. Visible and near-IR solid state luminescence spectra were collected on complexes 3, 4, 5, 6, 8, 8′, 9, 12, and 13 and characteristic terpyridine sensitized luminescence was observed.

RE-p-halobenzoic acid–terpyridine complexes, part III: structural and supramolecular trends in a series of p-iodobenzoic acid rare-earth hybrid materials

A series of twenty-one new rare-earth p-iodobenzoic acid complexes, [RE(L1)3(L2)(H2O)]2 (RE = La3+ (1) Ce3+ (2)), [RE(L1)3(L2)]2·H2O (RE = Ce3+ (2′), Pr3+ (3), Nd3+ (4), Sm3+ (5)), Eu3+ (6), Gd3+ (7), Tb3+ (8), Dy3+ (9), Ho3+ (10), Er3+ (11), Tm3+ (12), Yb3+ (13), Lu3+ (14), Y3+ (15)), [RE(L1)3(L2)(H2O)]2 (RE = Yb3+ (13′), Lu3+ (14′), Y3+ (15′)), and RE2(L1)4(L2)2(Ox) (RE = Er3+ (11′), Tm3+ (12′)); L1: p-iodobenzoic acid; L2: 2,2′:6′,2′′-terpyridine; Ox: oxalic acid, have been hydrothermally synthesized and structurally characterized by single crystal and powder X-ray diffraction. The series includes binuclear complexes [(La3+–Ce3+), (Ce3+–Y3+)], mononuclear complexes (Yb3+–Y3+), and oxalate-bridged binuclear complexes (Er3+–Tm3+), formed as a result of in situ ligand synthesis. All twenty-one complexes feature halogen- and π-based supramolecular interactions which assemble the molecular complexes into one, two, and three dimensions. Solid-state visible and near-IR luminescence spectra were collected on complexes 5, 6, 8, 9, 12, and 13 and characteristic emission was observed. The local coordination geometry over the p-iodobenzoic acid series were analyzed and then compared to the previously described and characterized RE-p-chlorobenzoic acid and RE-p-bromobenzoic acid analogues. Additionally, structural trends and supramolecular motifs were extracted from this series of materials and compared with the previously reported p-chloro- and p-bromo materials.

Utilizing bifurcated halogen-bonding interactions with the uranyl oxo group in the assembly of a UO2–3-bromo-5-iodo­benzoic acid coordination polymer

The synthesis and crystal structure of a new uranyl coordination polymer featuring 3-bromo-5-iodobenzoic acid is described and the luminescent and vibrational properties of the material have been explored. Compound (1), [UO2(C7H3BrIO2)2]n, features dimeric uranyl units chelated and then linked by 3-bromo-5-iodobenzoic acid ligands to form a one-dimensional coordination polymer that is subsequently assembled via bifurcated halogen-bonding interactions with uranyl oxo atoms to form a supramolecular three-dimensional network. The asymmetric, bifurcated halogen-bonding interaction in (1) is notable as it represents the first observation of this synthon in a uranyl hybrid material. Raman and IR spectroscopy showed that halogen-bonding interactions with the uranyl oxo atoms result in small shifts in υ1 and υ3 frequencies, whereas luminescence spectra collected at an excitation wavelength of 420 nm reveal partially resolved uranyl emission.

Hybrid Lanthanide–Actinide Peroxide Cage Clusters

A cage cluster consisting of 31 uranyl and 9 Sm(3+) polyhedra self-assembles in an alkaline aqueous peroxide solution and crystallizes (U31Sm9). Trimers of Sm(3+) polyhedra are templated by μ3-η(2):η(2):η(2)-peroxide groups and link to oxo atoms of uranyl ions. Three such trimers link into a ring through uranyl hexagonal bipyramids, and these are attached through six polyhedra to a unit consisting of 21 uranyl hexagonal bipyramids to complete the cage. Luminescence spectra collected with an excitation wavelength of 420 nm reveal fine structure, which is not observed for a cluster containing only uranyl polyhedra.

Eight rare earth metal organic frameworks and coordination polymers from 2-nitroterephthlate: syntheses, structures, solid-state luminescence and an unprecedented topology

Eight novel lanthanide metal organic frameworks (MOFs) and coordination polymers (CPs), La2(NTA)3(OH2)6 (1), [Nd(NTA)(HNTA)(OH2)2]·3H2O (2), [Nd2(NTA)3(OH2)2](H2O)3·2H2O (3), and [Ln2(NTA)3(OH2)2](H2O)2 (Ln = Sm (4), Eu (5), Gd (6), Tb (7), Er (8)), (H2NTA = 2-nitroterephthalic acid), have been synthesized under hydrothermal and slow evaporation conditions. The compounds are characterized by X-ray crystallography, elemental analyses, infrared spectroscopy and thermogravimetric analyses (TGA). Compounds 1–8 feature varying coordination modes of the NTA ligand, including two modes that are being reported for the first time. Compound 2 was crystallized by slow evaporation and features a supramolecular 3-D framework involving H-bonds and π–π stacking interactions. In compounds 1 and 3–8, which were made under hydrothermal conditions, non-covalent interactions are secondary and the 3-D network is built from strong covalent bonds. Compounds 1, 3, and 4–8 form a 3,4,5-c network having point symbol {4∧2.6}2{4∧2.8∧4}{4∧3.6.8∧6}2, a 4,4,6-c net with point symbol {4∧2.8∧4}{4∧4.6∧2}2{4∧8.6∧7}2 and an unprecedented 4,4,6-c net with point symbol {4∧2.6∧4}{4∧3.6∧3}2{4∧8.6∧6.8}2 respectively. The topologies are further simplified as parallel packing of rod-like SBUs; 1 and 2 form a distorted pcu network, 3 forms the nbo topology and 4–8 form the hex type topological network. From the crystal structure, solvent accessible voids for 2 and 3 are 138 A3 [13%] and 864 A3 [25%] of unit cell volume respectively. TGA data suggest that the framework in compounds 1, 2, 3, 5 and 7 are thermally stable up to 300 °C. Photoluminescence studies on compounds 5 and 7 indicate that NTA does not efficiently sensitize Eu3+ and Tb3+ emission due to alternate deactivation pathways available to the ligand. However, direct excitation in the visible region at 466 nm leads to red emission at room temperature in compound 5, the spectral profile of which suggests a lowering of the crystal field symmetry around Eu3+ and a quadrupolar contribution to the 5D0 → 7F2 peak. Emission from direct excitation of Tb3+ however is still quenched possibly due to back energy transfer to the ligand. This study is the second and most extensive report of lanthanide-based coordination networks involving nitroterephthalic acid and demonstrates its versatility as a building block for Ln-CPs and Ln-MOFs whose structures can be simplified as linked rod-shaped SBUs.

Survey concerning electronic textbooks

Purpose – A survey of students in different undergraduate majors and years asked where they bought their textbooks, the types of electronic devices they used, and their post-class use of textbook material. The research goal was to determine the groups of students likely most receptive to e-textbooks and to assess the potential environmental benefits of e-textbook adoption. The paper aims to discuss these issues. Design/methodology/approach – The student population of freshmen and juniors registered at Michigan State University were surveyed via e-mail/online in summer 2010. 477 freshmen (7.8 percent of surveyed) and 652 juniors (10.2 percent of surveyed) responded. Responses were grouped together into seven categories by student major. Findings – Surveyed students used far more print textbooks than e-textbooks. Laptops were the dominant student device and their future promise for e-textbook use is limited. The higher-than-expected rate of e-waste generation by students indicates that the environmental ben...