A Reproducible and Effective Technique for Coronary Sinus Injury Repair.

Objective: Coronary sinus injury related to the use of a retrograde cardioplegia catheter is a rare but potentially life-threatening complication with mortality reported as high as 20%. We present a series of iatrogenic coronary sinus injuries as well as an effective method of repair without any ensuing mortality. Methods: There were 3,004 cases that utilized retrograde cardioplegia at our institution from 2007 to 2018. Of these, 15 patients suffered a coronary sinus injury, an incidence of 0.49%. A pericardial roof repair was performed in 14 cases in which autologous pericardium was sutured circumferentially to normal epicardium around the injury with purified bovine serum albumin and glutaraldehyde injected into the newly created space as a sealant. Incidence of perioperative morbidity and mortality, operative time, and length of stay were collected. Results: In our series, there were no intraoperative or perioperative mortalities. Procedure types included coronary artery bypass grafting (CABG), valve replacement and repair, or combined CABG and valve procedures. Median (interquartile range) cross-clamp time was 100 (88 to 131) minutes, cardiopulmonary bypass duration was 133 (114 to 176) minutes, and length of stay was 6 (4 to 8) days. None of the patients returned to the operating room for hemorrhage, and there were no complications associated with the repair of a coronary sinus injury when using the pericardial roof technique. Conclusions: Coronary sinus injuries can result in difficult to manage perioperative bleeding and potentially lethal consequences from cardiac manipulation. Our series supports the pericardial roof technique as an effective solution to a challenging intraoperative complication.

Monitoring helical twists and effective molarities in dinuclear triple-stranded lanthanide helicates.

The replacement of terminal benzimidazole-pyridine binding units in the neutral di-tridentate segmental ligand L1 with phenanthroline in L10 reduces the number of torsional degrees of freedom by two units. Reactions of these ligands with trivalent europium or lutetium cations yield structurally similar self-assembled dinuclear triple-stranded [Ln2(Lk)3]6⁺ complexes, thus demonstrating that the increased rigidity of the strand in L10 is compatible with its helical twist. With the larger lanthanum cations, the metallic coordination spheres are completed with two terminal axial triflate counter-anions to give [La2(L10)3(CF3SO3)2]4⁺. Thermodynamic investigations in acetonitrile confirm the minor constraints produced by the planar phenanthroline unit in L10 leading to comparable effective molarities EMEu,L1 ≈ EMEu,L10 = 10-3.9(4) M with mid-range EuIII cations. The striking minute effective molarities EMLn,Ln-2H ≈ 10⁻6-10⁻9 M obtained upon the replacement of terminal phenanthrolines with structurally analogous fused hydroxyquinolines in L9 can be thus unambiguously assigned to solvation effects, a new tool for controlling complexity in metal-induced self-assembly processes.

Allosteric effects in binuclear homo- and heterometallic triple-stranded lanthanide podates.

This work illustrates a simple approach for deciphering and exploiting the various free energy contributions to the global complexation process leading to the binuclear triple-stranded podates [Ln(2)(L9)](6+) (Ln is a trivalent lanthanide). Despite the larger microscopic affinities exhibited by the binding sites for small Ln(3+), the stability constants measured for [Ln(2)(L9)](6+) decrease along the lanthanide series; a phenomenon which can be ascribed to the severe enthalpic penalty accompanying the intramolecular cyclization around small Ln(III), combined with increasing anticooperative allosteric interligand interactions. Altogether, the microscopic thermodynamic characteristics predict ß(1,1,1)(La,Lu,L9)/ß(1,1,1)(Lu,La,L9) = 145 for the ratio of the formation constants of the target heterobimetallic [LaLu(L9)](6+) and [LuLa(L9)](6+) microspecies, a value in line with the quantitative preparation (>90%) of [LaLu(L9)](6+) at millimolar concentrations. Preliminary NMR titrations indeed confirm the rare thermodynamic programming of a pure heterometallic f-f' complex.

Engineering new metal-organic frameworks built from flexible tetrapyridines coordinated to Cu(II) and Cu(I).

A series of new metal-organic frameworks have been constructed by the coordination of Cu(II) and Cu(I) with pentaerythrityl tetrakis(4-pyridyl) ether (1 = PETPE), a flexible tetradentate ligand. Networks derived from Cu(OOCCH(3))(2), Cu(NO(3))(2), and CuBF(4) proved to have different topologies (diamondoid, PtS, and SrAl(2), respectively). This reflects (1) the ability of PETPE (1) to adopt diverse conformations and (2) the varied geometries of complexes of Cu(II) and Cu(I). Extended PETPE (2), a tetrapyridine with phenyl spacers inserted into the pentaerythrityl core of PETPE (1), yielded an expanded version of the PtS network derived from simple PETPE (1) and Cu(NO(3))(2). However, increases in the ability of the network to accommodate guests were largely offset by interpenetration of independent networks. Attempts to thwart interpenetration by converting ligand 2 into methyl-substituted derivative 3 led to the construction of networks with alternative topologies. In particular, the reactions of ligand 3 with both Cu(II) and Cu(I) yielded isostructural Pt(3)O(4) networks, despite the preference of the two oxidation states for coordination spheres with different geometries. Together, these observations demonstrate that PETPE (1) and related compounds are useful ligands for constructing metal-organic frameworks, with a distinctive ability to accommodate a single metal in different oxidation states, as well as to adapt to a metal in a single oxidation state but with different counterions or secondary ligands.

Structural, spectroscopic, and thermodynamic consequences of anti-chelate effect in nine-coordinate lanthanide podates.

The connection of three tridentate 2,6-bis(1-ethyl-benzimidazol-2-yl)pyridine binding units to an extended sulfur-containing tripodal anchor in the ligand L9 yields nine-coordinate podates [Ln(L9)](3+) upon reaction with trivalent lanthanides, Ln(III). Structural analysis of [Eu(L9)](ClO(4))(3) in the solid state with the help of the bond valence method shows that the peripheral ethyl groups are responsible for a specific distortion of the triple-helical structure, which allows a closer approach of the nitrogen donors toward the central metal, while minimizing interstrand repulsion. The consequences of this distortion on the Eu(III) luminescent probe are investigated by high-resolution emission spectroscopy, while paramagnetic NMR data collected in acetonitrile demonstrate that [Ln(L9)](3+) adopts a single relaxed C(3)-symmetrical structure along the complete lanthanide series. The persistence of the triple-helical structure in solution is obtained at the cost of severe constraints in the helically wrapped organic tripod, which strongly disfavor intramolecular cyclization processes. The resulting antichelate effect can be exploited for the selective preparation of polynuclear complexes with tripodal ligands.