Stereoselective Asymmetric Syntheses of Molecules with a 4,5-Dihydro-1H-[1,2,4]-Triazoline Core Possessing an Acetylated Carbohydrate Appendage: Crystal Structure, Spectroscopy, and Pharmacology.

A new series of chiral 4,5-dihydro-1H-[1,2,4]-triazoline molecules, featuring a ß-ᴅ-glucopyranoside appendage, were synthesized via a 1,3-dipolar cycloaddition reaction between various hydrazonyl chlorides and carbohydrate Schiff bases. The isolated enantiopure triazolines (8a-j) were identified through high-resolution mass spectrometry (HRMS) and vibrational spectroscopy. Subsequently, their solution structures were elucidated through NMR spectroscopic techniques. Single-crystal X-ray analysis of derivative 8b provided definitive evidence for the 3-D structure of this compound and revealed important intermolecular forces in the crystal lattice. Moreover, it confirmed the (S)-configuration at the newly generated stereo-center. Selected target compounds were investigated for anti-tumor activity in 60 cancer cell lines, with derivative 8c showing the highest potency, particularly against leukemia. Additionally, substituent-dependent anti-fungal and anti-bacterial behavior was observed.

Metalated Porphyrin Stable Free Radicals: Exploration of Electron Spin Communication and Dynamics.

Switchable coupling between two qubits is important for quantum information science (QIS). As a proof of concept, a series of mesosubstituted porphyrins have been synthesized with a (2,2,6,6-tetramethylpiperidin-1-yl)oxyl stable free radical (SFR) appended and metalated with Cu(II), Ni(II), and Zn(II) in order to explore the interaction between the SFR doublet state and metalloporphyrin. The spin state of the porphyrin varies upon metal insertion, where Zn(II) is a diamagnetic metal, Cu(II) is paramagnetic, and Ni(II) can be switched from a diamagnetic square-planar structure to a paramagnetic octahedral state by complexation with a solvent (i.e., pyridine or tetrahydrofuran). Time-resolved electron paramagnetic resonance (EPR) measurements reveal that upon photoexcitation, the Zn(II) and free-base porphyrin species demonstrate different magnetic exchange regimes between the porphyrin triplet excited states and the SFR doublet state, with the Zn derivative populating a quartet state (i.e., moderate magnetic exchange), whereas the free-base derivative remains a triplet (i.e., weak magnetic exchange). Transient absorption measurements corroborate the TREPR results, demonstrating a 66% increase in the singlet excited-state decay rate due to enhanced intersystem crossing for the Zn(II) derivative in comparison to a modest 14% enhancement for the free-base porphyrin. These results enable the realization of a switchable qubit coupler, depending upon Zn metal insertion to the free-base porphyrin, which has potential QIS applications.

Building from Ga-Porphyrins: Synthesis of Ga-Acetylide Complexes Using Acetylenes and Polyynes.

Multidimensional, conjugated building blocks have been formed through the axial coordination of polyynes to the central Ga atom of tetraarylporphyrins. Electron deficient pentafluorophenyl substituents in the meso-positions provide more stable σ-acetylide complexes to Ga than analogous structures with tert-butylphenyl groups. Mono-, di-, and triynes have been used, including a pyridyl endcapped diyne that allows for formation of porphyrin triads through coordination of the pyridyl ligand to a Ru porphyrin.

Copper(II) thiaethyneporphyrin and copper(II) 21-phosphoryl N-confused porphyrin hybrids. intramolecular copper(II)-carbon interaction inside of a porphyrinoid surrounding.

Stabilization of unusual organocopper(II) species via the very efficient protection of the copper(II)-carbon bond has been achieved encapsulating the copper(II) center in the coordination core of suitably constructed carbaporphyrinoids. Copper(II) was inserted into hybrid N-confused porphyrins which contain 21-diphenylphosphoryl-, 21-diphenylthiophosphoryl-, or 21-phosphinodithioic substituents or into 20-thiaethyneporphyrin, an aromatic porphyrinoid, which combines two structural motifs of 21-thiaporphyrin and ethyne. Two distinctly different types of the copper(II)-carbon bond have been detected. Copper(II) hybrid N-confused porphyrins reveal the η(1)-C(21) side-on coordination. The unprecedented equatorial metal(II)···Î·(2)-CC interaction has been trapped in a copper(II) thiaethyneporphyrin surrounding.

Regioselective phosphorylation and thiophosphorylation of N-confused porphyrin: a route to hybrid carbaporphyrinoids.

N-confused porphyrin (NCP) undergoes controlled regioselective phosphorylations at the inner, outer or both carbon atoms of the inverted pyrrole ring. Reactivity centered at the internal carbon atom is enhanced in the Ag(III) NCP's whereas the preference for perimeter substitution is characteristic of free base NCP. The addition of S(8) resulted in the formation of thio-derivatives containing 21-diphenylthiophosphoryl or 21-phosphinodithioic substituents.

Organocopper(II) complex of 21-diphenylphosphoryl-carbaporpholactone hybrid: a side-on coordination mode of copper(II).

The diphenylphosphoryl-carbaporpholactone hybrid is a new aromatic porphyrinoid, which preserves the essential features of the carbaporpholactone frame and provides a suitable environment allowing stabilization of the organocopper(II) complex affording a peculiar side-on coordination of copper(II).

Regioselective amination of carbaporpholactone and N-confused porphyrin.

An efficient route to the direct amination at the inner carbon of carbaporpholactone is reported. A regioselectivity of substitution is enforced by activation of the embedded furanone fragment due to coordination of the highly oxidized silver(III) cation. A stepwise oxidation of the dimethylamine derivative leads to the internally bridged carbaporpholactones which contain respectively [5.7.5] tricyclic or [5.7.5.7.5] pentacyclic rings. The analogous reactivity of N-confused porphyrin has been also explored.

Electronically Tuned Asymmetric meso-Substituted Porphyrins for p-Type Solar Cells.

A series of electronically tuned asymmetric porphyrins have been synthesized for use in p-type solar cells. The porphyrin derivatives were strategically designed with electron-withdrawing capability and an electronic dipole gradient to aid in electron-harvesting capacity from a nickel oxide cathode. Specifically, the porphyrins were substituted at the meso position with different arrangements of the electron-withdrawing pentafluorobenzene moiety, electron-donating/coordinating 4-pyridyl ligand, and an electron withdrawing/synthetically modifiable 4-cyanophenyl unit. Two distinct free-base porphyrins were synthesized, one of which was further metallated with nickel(II). The porphyrins were fully characterized and their electronic properties explored experimentally by electrochemistry, and both steady state and time-resolved spectroscopy. Finally, the porphyrins were incorporated into a p-type solar cell device utilizing NiO as the cathode, and demonstrating a preliminary maximum performance of η(%)=0.082 and IPCEMAX (%)=26.0 without co-sensitization.