Control of Self-Assembly through the Influence of Terminal Hydroxymethyl Groups on the Metal Coordination of Pyrimidine−Hydrazone Cu(II) Complexes

Abstract

The synthesis and characterization of 6-hydroxymethylpyridine-2-carboxaldehyde (2-methyl-pyrimidine-4,6-diyl)bis(1-methylhydrazone) (1) is reported. Ligand 1 was designed as a ditopic pyrimidine-hydrazone molecular strand with hydroxymethyl groups attached to the terminal pyridine rings. Coordination of 1 with Cu(ClO(4))(2) x 6 H(2)O or Cu(SO(3)CF(3))(2) x 4 H(2)O in a 1:2 molar ratio resulted in the dinuclear Cu(II) complexes [Cu(2)1(CH(3)CN)(4)](ClO(4))(4) x CH(3)CN (4) and [Cu(2)1(SO(3)CF(3))(2)(CH(3)CN)(2)](SO(3)CF(3))(2) x CH(3)CN (5). X-ray crystallography and (1)H NMR NOESY experiments showed that 1 adopted a horseshoe shape with both pyrimidine-hydrazone (pym-hyz) bonds in a transoid conformation, while 4 and 5 were linear in shape, with both pym-hyz bonds in a cisoid conformation. Coordination of 1 with Cu(ClO(4))(2) x 6 H(2)O or Cu(SO(3)CF(3))(2) x 4 H(2)O in a 1:1 molar ratio resulted in three different bent complexes, [Cu(1H)(ClO(4))(2)](ClO(4)) (6), [Cu(1H)(CH(3)CN)](ClO(4))(3) x 0.5 H(2)O (7), and [Cu1(SO(3)CF(3))](2)(SO(3)CF(3))(2) x CH(3)CN (8), where the pym-hyz bond of the occupied coordination site adopted a cisoid conformation, while the pym-hyz bond of the unoccupied site retained a transoid conformation. Both 6 and 7 showed protonation of the pyridine nitrogen donor in the empty coordination site; complex 8, however, was not protonated. A variety of Cu(II) coordination geometries were seen in structures 4 to 8, including distorted octahedral, trigonal bipyramidal, and square pyramidal geometries. Coordination of the hydroxymethyl arm in the mononuclear Cu(II) complexes 6, 7, and 8 appeared to inhibit the formation of a [2 x 2] grid by blocking further access to the Cu(II) coordination sphere. In addition, the terminal hydroxymethyl groups contributed to the supramolecular structures of the complexes through coordination to the Cu(II) ions and hydrogen bonding.

Kontrollierte Faltungs‐, Bewegungs‐ und konstitutionelle Dynamik in polyheterocyclischen molekularen Strängen

“…Wir möchten hier nur sehr knapp eine Auswahl nennen und verweisen den Leser für weitere Informationen auf die angegebenen Referenzen. Von anderen Forschungsgruppen untersuchte dynamische Bewegungssysteme und/oder Konformationsänderungen umfassen: 1) das helikale Umwickeln von Quinquepyridin, Bishydrazonen, Pentaoxyethylen sowie anderen Liganden um Metallionen;– 2) Bewegungsprozesse, Schalter, Metallkomplexe und Sensoren auf Basis von Hydrazonen;, 3) Faltung‐Entfaltung eines Terpyridin‐Komplexes; 4) die Ausweitung von helikalen Molekülen durch die Bildung von doppelhelikalen Dimeren; 5) das lösungsmittelinduzierte oder Chaperon‐assistierte Falten und Entfalten oder pH‐modulierte Schalter in helikalen Strängen (Änderung der helikalen Steigung); 6) eine sprungfederartige Bewegung (partielles Entfalten und Änderung der Helix‐Gangweite; 7) eine temperaturkontrollierte Steigerung der Helix‐Laufweite; 8) Metallionen‐assistierte Prozesse;– 9) eine oligomere o ‐Phenylenhelix, die dynamische Bewegung als Reaktion auf eine Änderung des Redoxzustands eingeht; 10) reversibles Abwickeln einer Oligo‐Resorcinol‐Doppelhelix; 11) das Falten und Entfalten von Poly(ethylenglycol) und Poly(ethylenimin) in Lösung; 12) das anioneninduzierte Falten von aromatischen Amid‐basierten Oligomeren; 13) das konformative Schalten von phenolischen Oligoamiden (linear zu gebogen); 14) photoschaltbare Foldamere;, 15) das säureinduzierte molekulare Falten und Entfalten von Pyrimidin‐Amid‐basierten Oligomeren; 16) das durch Komplexierung induzierte Entfalten von heterocyclischen Harnstoffderivaten; 17) das Falten/Entfalten von elektrochemisch adressierbaren Molekülen; 18) das lösungsmittelabhängige Falten/Entfalten von oligomeren Cholaten oder Foldameren; 19) das reversible Entfalten einer Helix einschließlich Depolymerisierung; 20) das stimulierte Falten und Entfalten von Polymeren; 21) das per pH‐Wert adressierbare Umwickeln oder Falten/Entfalten von DNA i‐Motiven; 22) die lösungsmittelinduzierte Konformationsänderung von Poly( m ‐ethinylpyridinen); 23) die akkordeonartige Oszillation von Helices oder molekularen Sprungfedern; und 24) die hydrazonbasierten zwei‐ und mehrkernigen Komplexe (oft erzeugt durch Entwindung von gebogenen Liganden) –. Übersichtsartikel zu abstimmbaren helikalen Strukturen und die funktionelle ...…”

Metal-Induced Isomerization of a Molecular Strand Containing Contradictory Dynamic Coordination Sites

“…Despite the change in shape of L1 caused by protonation, many of the signals in its 1 H and 13 C NMR spectra were similar to those of other native and unprotonated pym-hyz ligands. 1,8,9 The H10 signal of the protonated form of L1 was located at 7.43 ppm, which was typical of pym protons adjacent to transoid pym-hyz linkages, despite H10 being between one transoid and one cisoid pymhyz linkage. The chemical shifts of the hyz imine protons and the terminal py protons were also similar to those of uncoordinated pym-hyz ligands.…”

“…The terminal pym-hyz-py coordination sites of the complexes adopted linear cisoid−cisoid conformations, as seen previously for other pym-hyz based ligands ( Figure 4). 1,4,7,8 The formation of these horseshoe-shaped M n+ 3 L1A 3n complexes resulted in a number of diagnostic chemical shift changes in their 1 H NMR spectra. For example, in the 1 H NMR spectrum of each of the Pb 3 L1A 6 complexes, the H10 signal was shifted upfield from its chemical shift of 7.43 ppm in the protonated L1 spectrum to 6.65 ppm, due to the removal of the deshielding effects from the adjacent hyz linkage upon rotation of the transoid pym-hyz bond to a cisoid conformation.…”

Photochemical and Electrochemical Triggered Bis(hydrazone) Switch

“…[13] Examples of these light-driven machinesc an be found in compounds containing substituted double bonds like N=N present in azo compounds, [14] and C=Np resenti ni mines, oximes, [15] andh ydrazones. [20] The straightforwardm ethodology of hydrazone synthesis,b yt he condensation of hydrazine and aldehyde derivativeso ft he desired heterocyclic core, [21,22] makesthem very accessible. [20] The straightforwardm ethodology of hydrazone synthesis,b yt he condensation of hydrazine and aldehyde derivativeso ft he desired heterocyclic core, [21,22] makesthem very accessible.…”

“…[16] Amongt hese compounds, moleculars trands possessing alternating hydrazonea nd heterocyclic units such as pyrimidine, [17] pyridine, [18] and triazine [19] have attracted particular attention for their applicationsinthe development of nanometric devices. [20] The straightforwardm ethodology of hydrazone synthesis,b yt he condensation of hydrazine and aldehyde derivativeso ft he desired heterocyclic core, [21,22] makesthem very accessible.…”