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The self-assembly of 2,6-diformyl-4-methylphenol (DFMP) and 1-amino-2-propanol (AP)/2-amino-1,3-propanediol (APD) in the presence of copper(II) ions results in the formation of six new supramolecular architectures containing two versatile double Schiff base ligands (H3L and H5L1) with one-, two-, or three-dimensional structures involving diverse nuclearities: tetranuclear [Cu4(HL2−)2(N3)4]·4CH3OH·56H2O (1) and [Cu4(L3−)2(OH)2(H2O)2] (2), dinuclear [Cu2(H3L12−)(N3)(H2O)(NO3)] (3), polynuclear [Cu2(H3L12−)(H2O)(BF4)(N3)]·H2On (4), heptanuclear [Cu7(H3L12−)2(O)2(C6H5CO2)6]·6CH3OH·44H2O (5), and decanuclear [Cu10(H3L12−)4(O)2(OH)2(C6H5CO2)4] (C6H5CO2)2·20H2O (6). X-ray studies have revealed that the basic building block in 1, 3, and 4 is comprised of two copper centers bridged through one μ-phenolate oxygen atom from HL2− or H3L12−, and one μ-1,1-azido (N3−) ion and in 2, 5, and 6 by μ-phenoxide oxygen of L3− or H3L12− and μ-O2− or μ3-O2− ions. H-bonding involving coordinated/uncoordinated hydroxy groups of the ligands generates fascinating supramolecular architectures with 1D-single chains (1 and 6), 2D-sheets (3), and 3D-structures (4). In 5, benzoate ions display four different coordination modes, which, in our opinion, is unprecedented and constitutes a new discovery. In 1, 3, and 5, Cu(II) ions in [Cu2] units are antiferromagnetically coupled, with J ranging from −177 to −278 cm−1.

The iron (II) coordination compound, [Fe(3,6 pzdc)](H2O)22. (1) has been synthesized from a mixture of FeCl2.4H2O and pyridazinedicarboxylate (3,6 pzdc). The molecular structure of complex 1 was determined by single crystal X-ray diffraction study. It reveals that the dinuclear structure contains a pyridazine bridge in between the two metal centers. The variable temperature magnetic study results in g = 2.496(8), J = −2.50(8) cm−1, Ɵ = −0.1 K values, by fitting the magnetic data in a simple dinuclear Fe-Fe model which indicates that the major exchange pathway through the N-N bridge. Presence of dense H-bonding interaction leads to supramolecular network formation.

The reaction of 2,6-diformyl-4-methylphenol (DFMF) with 1-amino-2-propanol (AP) and tris(hydroxymethyl)aminomethane (THMAM) was investigated in the presence of Cobalt(II) salts, (X = ClO4−, CH3CO2−, Cl−, NO3−), sodium azide (NaN3), and triethylamine (TEA). In one pot, the variation in Cobalt(II) salt results in the self-assembly of dinuclear, tetranuclear, and H-bonding-directed polynuclear coordination complexes of Cobalt(III), Cobalt(II), and mixed-valence CoIICoIII: [Co2III(H2L−1)2(AP−1)(N3)](ClO4)2 (1), [Co4(H2L−1)2(µ3-1,1,1-N3)2(µ-1,1-N3)2Cl2(CH3OH)2]·4CH3OH (2), [Co2IICo2III(HL−2)2(µ-CH3CO2)2(µ3-OH)2](NO3)2·2CH3CH2OH (3), and [Co2IICo2III (H2L12−)2(THMAM−1)2](NO3)4 (4). In 1, two cobalt(III) ions are connected via three single atom bridges; two from deprotonated ethanolic oxygen atoms in the side arms of the ligands and one from the1-amino-2-propanol moiety forming a dinuclear unit with a very short (2.5430(11) Å) Co-Co intermetallic separation with a coordination number of 7, a rare feature for cobalt(III). In 2, two cobalt(II) ions in a dinuclear unit are bridged through phenoxide O and μ3-1,1,1-N3 azido bridges, and the two dinuclear units are interconnected by two μ-1,1-N3 and two μ3-1,1,1-N3 azido bridges generating tetranuclear cationic [Co4(H2L−1)2(µ3-1,1,1-N3)2(µ-1,1-N3)2Cl2(CH3OH)2]2+ units with an incomplete double cubane core, which grow into polynuclear 1D-single chains along the a-axis through H-bonding. In 3, HL2− holds mixed-valent Co(II)/Co(III) ions in a dinuclear unit bridged via phenoxide O, μ-1,3-CH3CO2−, and μ3-OH− bridges, and the dinuclear units are interconnected through two deprotonated ethanolic O in the side arms of the ligands and two μ3-OH− bridges generating cationic tetranuclear [Co2IICo2III(HL−2)2(µ-CH3CO2)2(µ3-OH)2]2+ units with an incomplete double cubane core. In 4, H2L1−2 holds mixed-valent Co(II)/Co(III) ions in dinuclear units which dimerize through two ethanolic O (μ-RO−) in the side arms of the ligands and two ethanolic O (μ3-RO−) of THMAM bridges producing centrosymmetric cationic tetranuclear [Co2IICo2III (H2L1−2)2(THMAM−1)2]4+ units which grow into 2D-sheets along the bc-axis through a network of H-bonding. Bulk magnetization measurements on 2 demonstrate that the magnetic interactions are completely dominated by an overall ferromagnetic coupling occurring between Co(II) ions.

Polynuclear coordination complexes result from the interplay between the arrangement of the binding sites of a ligand, and their donor content, and the coordination preferences of the metal ion involved. Rational control of the ligand properties, such as denticity, geometry, and size, can lead to large, and sometimes predictable, polynuclear assemblies. This Alcan Award Lecture highlights our \"adventures\" with polynucleating ligands over the last 25 years, with examples ranging from simple dinucleating to more exotic high-denticity ligands. Complexes with nuclearities ranging from 2 to 36 have been produced, many of which have novel magnetic, electrochemical, and spectroscopic properties. Self-assembly strategies using relatively simple \"polytopic\" ligands have been very successful in producing high-nuclearity clusters in high yield. For example, linear \"tritopic\" ligands produce M 9 (M = Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II)) [3 × 3], flat grid-like molecules, which have quantum dot-like arrays of nine closely spaced metal centers in electronic communication. Some of these grids are discussed in terms of their novel magnetic and electrochemical properties, and also as multistable nanometer-scale platforms for potential molecular device behaviour. Bigger ligands with extended arrays of coordination pockets, and the capacity to self-assemble into much larger grids, are highlighted to illustrate our current and longer term goals of generating polymetallic molecular two-dimensional layers on surfaces.Key words: Alcan Award Lecture, transition metal, polynuclear, structure, magnetism, electrochemistry, surface studies, molecular device.

Reduction of [( ) 2 ][As 6 ] 2 with triphenylantimony and tetrabutylammonium chloride produced the diradical 5,5'-bis(1,3,2,4-dithiadiazolyl) [ - ] in high yield as a black solid with widely ranging magnetic susceptibilities (e.g., 0.6 to 2.6 B ), which on oxidation with AsF 5 regenerated [( ) 2 ][AsF 6 ] 2 . The identity of [ - ] was established from EPR, vibrational, and mass spectra. Ab initio molecular orbital [MPW1PW91/6-311G(2df)] calculations show the lowest energy structure to consist of two coplanar rings separated by a C—C single bond (1.444 Å), reflected in the comparison of the vibrational spectra of the diradical with that of [( ) 2 ][AsF 6 ] 2 and the calculated spectra. Confidence in the calculated [MPW1PW91/6-311G(2df)] structure of the diradical is supported by the excellent agreement between the calculated and X-ray single crystal structure geometries of [ ] 2 and [( ) 2 ] 2+ in [( ) 2 ][AsF 6 ] 2 . The molecular orbitals indicate the diradical is essentially disjoint, confirmed by a very small (0.07 kJ mol –1 ) GVB-PP(TC-SCF)/6-311G* calculated singlet–triplet energy gap. Accordingly, the EPR spectrum of the diradical (in tetrahydrofuran, 293 K) shows a simple 3-line pattern (g = 2.0043, a( 14 N) = 1.11 mT) with no observable exchange coupling between the two radical centers. Mechanical grinding of the diradical results in a large increase in paramagnetism (e.g., from 1.03 to 2.55 B ) that is unprecedented in main group chemistry. The X-ray diffraction data of the ground and unground powder are consistent with a second order phase change on grinding. Attempts to obtain crystals of the diradical by sublimation led instead to numerous decomposition and rearrangement products, including 4-cyano-1,2,3,5-dithiadiazolyl [NC- ], monoclinic space group C2/c, a = 9.46(2) Å, b = 7.625(5) Å, c = 13.17(2) Å, = 107.94(4)°, Z = 8. The structure consists of axially symmetric, co-facial, cis dimers linked to form strands through two sets of C N – ···S + contacts. More efficient and larger scale preparations of [SNS][AsF 6 ] and [( ) 2 ][AsF 6 ] 2 are reported. Key words: 5,5'-bis(1,3,2,4-dithiadiazolyl), diradical, paramagnetism, mechanical grinding, second order phase change, 4-cyano-1,2,3,5-dithiadiazolyl.

Polynuclear coordination complexes result from the interplay between the arrangement of the binding sites of a ligand, and their donor content, and the coordination preferences of the metal ion involved. Rational control of the ligand properties, such as denticity, geometry, and size, can lead to large, and sometimes predictable, polynuclear assemblies. This Alcan Award Lecture highlights our \"adventures\" with polynucleating ligands over the last 25 years, with examples ranging from simple dinucleating to more exotic high-denticity ligands. Complexes with nuclearities ranging from 2 to 36 have been produced, many of which have novel magnetic, electrochemical, and spectroscopic properties. Self-assembly strategies using relatively simple \"polytopic\" ligands have been very successful in producing high-nuclearity clusters in high yield. For example, linear \"tritopic\" ligands produce M^sub 9^ (M = Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II)) [3 × 3], flat grid-like molecules, which have quantum dot-like arrays of nine closely spaced metal centers in electronic communication. Some of these grids are discussed in terms of their novel magnetic and electrochemical properties, and also as multistable nanometer-scale platforms for potential molecular device behaviour. Bigger ligands with extended arrays of coordination pockets, and the capacity to self-assemble into much larger grids, are highlighted to illustrate our current and longer term goals of generating polymetallic molecular two-dimensional layers on surfaces. [PUBLICATION ABSTRACT] Key words: Alcan Award Lecture, transition metal, polynuclear, structure, magnetism, electrochemistry, surface studies, molecular device.

The following sections are included: Convergent Self-assembly Introduction and overview Polytopic ligands for [n × n] square grids–design and self-assembly Thermodynamic aspects of the formation of convergent self-assembled grid architectures Ligands and Complexes Ditopic ligands and their complexes Homometallic complexes [2 × 2] grids with heterocyclic diazine (N2) bridging ligands Ditopic ligands with more remote coordination pockets Other polynuclear oligomers with remote ditopic ligands [2 × 2] grids with single atom μ-O and μ-S bridging ditopic ligands Ditopic hydrazone ligands with both μ-O or μ-NN bridging modes Higher order oligomeric clusters based on ditopic ligands Heterometallic [2 × 2] and mixed spin state grids Symmetric tritopic ligands and their complexes Homometallic [3 × 3] grids Heterometallic and mixed spin state [3 × 3] grids Tetratopic ligands and complexes Homometallic [4 × 4] grids Pentatopic ligands and their complexes Homometallic [5 × 5] grids Other Oligomers in the Assembly Process Incomplete grids, clusters and chains Nano-scale Molecular-Based Devices? Conclusions and Future Perspectives Acknowledgments References

The reactivity of some polyfunctional ligands has been investigated.One ligand, which forms binuclear complexes with ease, 1,4-(di-2'-pyridyl)-aminophthalazine, has been studied in some detail and provides the main topic of discussion in this thesis. Some previously unreported binuclear copper and mono - and binuclear cobalt and nickel complexes have been prepared. The majority of the copper complexes are thought to be five-coordinate while the cobalt complexes exhibit both four and six-coordination and the nickel complexes six-coordination.Some of the binuclear systems exhibit low magnetic moments which suggest the presence of metal-metal interaction.Another ligand, believed to be o-phenylene-bis(2-imidazoline) has been synthesized. Some of its complexes with nickel and cobalt salts have been investigated. These complexes exhibit four and six-coordination.

•Across 2,212 hospitals serving Medicare beneficiaries with CR-qualifying events, median CR enrollment was 19.6% and time to CR enrollment was 55 days.•CR metrics varied widely among hospitals nationally, and among peer hospitals in the same tier of cardiac care provided.•Hospital-level factors associated with poorer CR enrollment included for-profit ownership, regions other than the Midwest, rural location, and large hospital size. To inform the delivery of cardiac rehabilitation (CR) care nationwide at the hospital level, we described hospital-level variation in CR metrics, overall and stratified by the hospital's tier of cardiac care provided. This retrospective cohort analysis used Medicare fee-for-service (FFS) data (2018-2020), Parts A and B, and American Hospital Association (AHA) data (2018). We included beneficiaries with an acute myocardial infarction (AMI), percutaneous coronary intervention (PCI), or coronary artery bypass graft (CABG) in 2018, aged ≥65 years, and continuously enrolled in a FFS plan. We calculated hospital-level metrics for hospitals with ≥20 CR-qualifying events, which were identified using diagnostic/procedure codes. Claims for CR were identified by Healthcare Common Procedure Coding System (HCPCS) codes. We used multi-level models to examine patient- and hospital-level factors associated with CR metrics. Hospitals were stratified by tier of cardiac care provided (comprehensive, AMI/PCI, AMI-only care). Across the US, 2,212 hospitals treated individuals aged ≥65 years with a CR-qualifying event in 2018. By tier of cardiac care, 44.4% of hospitals provided comprehensive care, 31.2% provided AMI/PCI care, and 24.4% provided AMI-only care. Across all hospitals, there was substantial variation in CR enrollment (median 19.6%, interquartile range [IQR] = 7.0%, 32.8%). Among hospitals with enrollment (n = 1,866), median time to enrollment was 55.0 days (IQR = 41.0, 71.0), median number of CR sessions was 26.0 (IQR = 23.0, 29.0), and median percent completion was 26.0% (IQR = 10.5%, 41.2%). There was also substantial variation in CR performance metrics among hospitals within each tier of cardiac care (eg, median percent CR enrollment was 30.7% [IQR = 20.7%-41.3%] among comprehensive care hospitals, 18.6% [IQR = 9.5%-27.7%] among AMI/PCI hospitals, and 0.0% [IQR = 0.0%-7.7%] among AMI-only hospitals). In adjusted analyses, characteristics associated with lower odds of CR enrollment included patient-level factors (older age, female sex, non-White race or ethnicity), and hospital-level factors (for-profit ownership, regions other than the Midwest, rural location, medium/large hospital size). This is the first national, hospital-level analysis of CR metrics among Medicare beneficiaries. Substantial variation across hospitals, including peer hospitals within the same tier of cardiac care, indicates opportunities for hospital-level quality improvement strategies to improve CR referral and participation metrics.