The Hoopoe's Song

Dale, A. M.

doi:10.1017/s0009840x00173123

Cited by 2 publications

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“…These differences stem primarily from the nature of the macrocyclic ring. Cyclen adopts a square conformation, defined by Dale’s nomenclature as [3,3,3,3], in which the nitrogen atoms are located on the sides of the ring and each ethylene bridge adopts a gauche conformation. − It has been observed that if the conformation of cyclen is distorted into a another conformation significant loss of chelate stability can sometimes result . In the case of pyclen, however, the rigidity of the pyridine group dictates that one side of the macrocycle must incorporate 4 bonds and so a [3,3,3,3] conformation is impossible.…”

Section: Resultsmentioning

confidence: 99%

Solid State and Solution Dynamics of Pyridine Based Tetraaza-Macrocyclic Lanthanide Chelates Possessing Phosphonate Ligating Functionality (Ln-PCTMB): Effect on Relaxometry and Optical Properties

Kiefer

Woods

2009

Inorg. Chem.

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The macrocyclic ligand 3,6,9-tris(methylenebutyl phosphonic acid)-3,6,9-15-tetraazabicyclo [9.3.1] pentadeca-1(15),11,13-triene (PCTMB) was synthesized and complexes of Eu 3+ , Tb 3+ , and Gd 3+ studied by X-ray crystallography, luminescence, and relaxometry. In the crystal these complexes are dimeric and possess 8-coordinate Ln 3+ centers that are linked by bridging phosphonates. The rigidity introduced by the pyridyl nucleus forces the EuPCTMB and TbPCTMB to adopt a twisted snub disphenoid (TSD) coordination geometry. Examination of the 5 D 0 → 7 F 0 luminescent transition of EuPCTMB in the solid state confirmed the existence of a single distinct Eu 3+ coordination environment, whereas two Eu 3+ coordination environments were observed in aqueous solution. Lifetime analysis of aqueous TbPCTMB solutions determined that q = 0.1 and q = 1.0 for the two coordination environments and Stern-Volmer quenching constants (K SV τ = 1101 M −1 , K SV Φ = 40780 M −1 ) support the presence of a monomer/dimer equilibrium. Relaxivity studies of GdPCTMB in H 2 O/CH 3 OH exhibited a concentration dependency (0.02 mM -10.00 mM) ranging from r 1 = 7.0 mM −1 s −1 to 4.0 mM −1 s −1 consistent with the trend observed by luminescence.

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Section: Resultsmentioning

confidence: 99%

Solid State and Solution Dynamics of Pyridine Based Tetraaza-Macrocyclic Lanthanide Chelates Possessing Phosphonate Ligating Functionality (Ln-PCTMB): Effect on Relaxometry and Optical Properties

Kiefer

Woods

2009

Inorg. Chem.

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“…In the early days of conformational analysis, only symmetrical conformations of the medium-ring-cycloalkanes and derivatives were thought to be local minima or even TSs for conformational interconversion, 34 but this proved not to be the case. 35,36 Nowadays, it is well known that energy minima have to be carefully distinguished from TSs in the PEHS. Extensive searches of the conformational energy hypersurface for local minima should include the barriers separating pairs of conformations.…”

Section: Introductionmentioning

confidence: 99%

Ring inversion in 1,4,7 cyclononatriene and analogues: Ab initio and DFT calculations and topological analysis

2007

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The multidimensional conformational potential energy hypersurfaces (PEHSs) for cis-cis-cis 1,4,7 cyclononatriene (I), Tribenzocyclononatriene (TBCN) (II), and cis-cis-cis cyclic triglycine (III) were comprehensively investigated at the Hartree-Fock (HF/6-31G(d)) and density functional theory (B3LYP/6-31G(d,p)) levels of theory. The equilibrium structures, their relative stability, and the transition state (TS) structures involved in the conformational interconversion pathways were analyzed. Altogether, four geometries (two low-energy conformations and two transition states) were found to be important for a description of the conformational features of compounds I-III. B3LYP/aug-cc-pvdz//B3lYP/6-31G(d,p) and MP2/6-31G(d,p)//B3LYP/6-31G(d,p) single point calculations predict that the conformational interconversion between crown and twist forms requires 14.01, 26.71, and 17.79 kcal/mol for compounds I, II, and III, respectively, which is in agreement with the available experimental data. A topological study of the conformational PEHSs of compounds I-III was performed. Our results allow us to form a concise idea about the internal intricacies of the PEHSs of compounds I-III, describing the conformations as well as the conformational interconversion process in these hypersurfaces.

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The Hoopoe's Song

Cited by 2 publications

References 0 publications

Solid State and Solution Dynamics of Pyridine Based Tetraaza-Macrocyclic Lanthanide Chelates Possessing Phosphonate Ligating Functionality (Ln-PCTMB): Effect on Relaxometry and Optical Properties

Solid State and Solution Dynamics of Pyridine Based Tetraaza-Macrocyclic Lanthanide Chelates Possessing Phosphonate Ligating Functionality (Ln-PCTMB): Effect on Relaxometry and Optical Properties

Ring inversion in 1,4,7 cyclononatriene and analogues: Ab initio and DFT calculations and topological analysis

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