Isolating Equatorial and Oxo Based Influences on Uranyl Vibrational Spectroscopy in a Family of Hybrid Materials Featuring Halogen Bonding Interactions with Uranyl Oxo Atoms

Abstract

Abstract:The syntheses and crystal structures of six new complexes containing the UO 2 2+ cation, m-or p-halobenzoic acid ligands (where halogens are Cl and I), and the chelating Ndonors 1,10-phenanthroline (phen) (1, 3, 4, and 6) or 2,2′:6′,2′′-terpyridine (terpy) (7 and 9) are described and compared to UO 2 -m-bromo-and p-bromobenzoic analogues (2, 5, and 8) that have been reported previously. The spectroscopic properties (both vibrational and luminescence) for all nine complexes along with stretching and interaction force constants are reported and redshifts are noted as the electron-donating ability of the chelating N-donors increases. Single crystal X-ray diffraction analysis of these complexes shows that whereas inclusion of a chelating ligand (i.e. phen or terpy) in the uranyl first coor-

Probing hydrogen and halogen-oxo interactions in uranyl coordination polymers: a combined crystallographic and computational study

“…As the tectons and topologies observed in 1-4 have precedent in the extensive catalog of uranyl hybrid materials, 3,6,47 we focus our discussion on the modes of supramolecular assembly in these compounds. The supramolecular synthons observed in 1-4 all involve the nominally terminal uranyl oxo atoms, which can be engaged for assembly as we have demonstrated in multiple recent studies, 13,14,16,17 respectively. As there is an increase in halogen polarizability (Br<I) between 3 and 4, halogen bond strengths are not expected to be 'identical,' thus highlighting a limitation with our crystallographic efforts to gauge strengths of halogen-oxo interactions.…”

“…The uranyl cation is known to feature three characteristic vibrational modes: a symmetric stretching mode (1, 860-880 cm -1 , Raman active), a bending mode (2, 200-210 cm -1 , infrared active), and an asymmetric stretching mode (3, 930-960 cm -1 , infrared active), [48][49][50] and the frequencies of these vibrational modes, in particular 1 and 3, provide valuable spectroscopic information about relative strengths of U=O bonds (which are affected by halogen-oxo interactions). 16,17,27 A look at the Raman and IR spectra of compounds 3 and 4 reveals redshifts (6 cm -1 in the Raman and 11 cm -1 in the IR) with respect to the miodo compound (4) when comparing to the m-bromo compound (3) ( Figure 6). These findings qualitatively illustrate that the iodo-oxo interaction in 4 has a greater effect on the uranyl oxo group, and also suggest that the oxo interactions in 3 and 4 may not be of 'equivalent strength', as suggested by crystallography.…”

“…[1][2][3][4][5][6][7][8][9][10][11] This approach is predicated upon the directed assembly of tectons into crystalline architectures via attractive, noncovalent synthons, and utilization within uranyl hybrid materials has necessitated the development of a hierarchy of acceptordonor pairing preferences based on a detailed knowledge of the relationship between intra-and intermolecular interactions. 12 Recently, our group has been investigating the potential for crystal engineering to support engagement of the nominally terminal uranyl oxo groups, [13][14][15][16][17] and here we continue these efforts, employing hydrogen and halogen bonding for assembly and then describing uranyl oxo atom behavior as a synthon acceptor site. Development of a hierarchy of uranyl acceptor-donor pairing preferences requires a metric for adjudicating interaction strengths, which can then be qualitatively applied to judging which synthon acceptor and donor sites are 'best'.…”

Restricted Speciation and Supramolecular Assembly in the 5f Block

“…Using two sets of isomorphous complexes, differing only in halogen atom at the periphery of the tectons, means of assembly were evaluated and results indicated that inclusion of more electron donating N‐donor ligand (i.e. 2,2′:6′,2′′‐terpyridine, rather than 1,10‐phenanthroline) further facilitates halogen bonding at the uranyl oxo atoms . In this study, the spectroscopic manifestations of oxo atom participation in halogen bonding were also explicitly explored and compared to effects that result from equatorial electron donation.…”

“…2,2':6',2''-terpyridine, rather than 1,10-phenanthroline) further facilitates halogen bondinga tt he uranyl oxo atoms. [32] In this study,t he spectroscopic manifestations of oxo atom participation in halogen bonding were also explicitly explored and compared to effects that result from equatorial electron donation. Whereas structural resultsi ndicated there wasa ni nterplay between the chelating ligands and benzoic acid groups featuring halogens at the periphery, the polarizabilityoft he selected halogena tom was again found to be mosti mportant for driving the oxo engagement process, and theser esultsr un counter to spectroscopic analysisw hich demonstrates that vibrational (and luminescence) spectra are most impacted by the electrond onating capability of the equatorial ligands.…”