Ferrocene-Containing Acylhydrazone Receptors: Synthesis, Structures and Electrochemical Anion Recognition Characteristics

Ferrocene-containing redox receptors bearing the 2-(quinolin-8-yloxy)acetohydrazide (qa) moiety on one arm, [Fe(Cpqa)Cp], or two arms, [Fe(Cpqa)2], have been synthesised and the X-ray crystal structure of [Fe(Cpqa)2] determined. [Fe(Cpqa)2] can sense H2PO−4 both electrochemically and selectively even in the presence of a large excess of Cl− and ClO−4.

Crystal structure of (8-hydroxy-5-nitroquinolinium) perchlorate – 8-hydroxy-5-nitroquinoline (1/1), C18H13ClN4O10

C18H13ClN4O10, monoclinic, P21/c (no. 14), a = 21.009(9) Å, b = 9.474(4) Å, c = 9.747(4) Å, β = 98.360(9)°, V = 1919.4(14) Å3, Z = 4, R gt(F) = 0.0560, wR ref(F 2) = 0.1752, T = 293 K.

Cystine-derived bis-naphthalimides as stimuli-responsive fluorescent gelators

Stimuli-responsive fluorescence modulation of two cystine-derived bis-naphthalimide gelators was demonstrated using fluoride/tetrafluoroborate anions as the chemical inputs.

(E)-N′-(3,4,5-Trimethoxybenzylidene)-2-(8-quinolyloxy)acetohydrazide methanol solvate

In the title compound, C₂₁H₂₁N₃O₅·CH₄O, the quinoline plane and the benzene ring form a dihedral angle of 3.6 (2)°. The methanol solvent mol­ecule is linked with the acetohydrazide mol­ecule via O—H⋯N and N—H⋯O hydrogen bonds. In the crystal structure, weak inter­molecular C—H⋯O hydrogen bonds help to consolidate the crystal packing, which also exhibits π–π inter­actions, as indicated by short distances of 3.739 (4) Å between the centroids of the aromatic rings.

(E)-N′-(5-Chloro-2-hydroxybenzylidene)-4-(8-quinolyloxy)butanohydrazide monohydrate

The crystal of the title Schiff base compound, C₂₀H₁₈ClN₃O₃·H₂O, was twinned by a twofold rotation about (100). The asymmetric unit contains two crystallographically independent mol­ecules with similar conformations, and two water mol­ecules. The C=N—N angles of 115.7 (6) and 116.2 (6)° are significantly smaller than the ideal value of 120° expected for sp²-hybridized N atoms and the dihedral angles between the benzene ring and quinoline ring system in the two mol­ecules are 52.5 (7) and 53.9 (7)°. The mol­ecules aggregate via C—Cl⋯π and π–π inter­actions [centroid–centroid distances = 3.696 (5)–3.892 (5) Å] and weak C—H⋯O inter­actions as parallel sheets, which are further linked by water mol­ecules through N—H⋯O and O—H⋯O hydrogen bonds into a supra­molecular two-dimensional network.

(E)-N'-(2,5-Dimethoxy-benzyl-idene)-2-(8-quinol-yloxy)acetohydrazide methanol solvate

The two mol-ecules in the asymmetric unit of the title compound, C(20)H(19)N(3)O(4)·CH(4)O, are paired via O-H⋯(O,N), N-H⋯O, and C-H⋯O hydrogen bonds. The mol-ecular skeleton of the acetohydrazide mol-ecule is close to planar; the benzene and quinoline mean planes form a dihedral angle of 3.9 (3)°. The crystal packing exhibits weak inter-molecular C-H⋯O hydrogen bonds and π-π inter-actions, indicated by short distances of 3.668 (3) Å, between the centroids of N-containing six-membered rings from neighbouring acetohydrazide mol-ecules.

(E)-N'-(4-Pyridylmethyl-ene)-4-(8-quinol-yl-oxy)butanohydrazide 0.25-hydrate

The asymmetric unit of the title compound, C₁₉H₁₈N₄O₂·0.25H₂O, contains two organic mol­ecules and a solvent water mol­ecule with 50% occupancy. The two molecules differ in their conformations: in one mol­ecule it is (+)gauche-trans-trans-(+)gauche-trans, whereas in the other it is (−)gauche-trans-trans-(−)gauche-trans. The dihedral angles between the pyridine ring and the quinoline ring system are 67.4 (3) and 68.0 (2)°. Mol­ecules are linked into a supra­molecular two-dimensional array via N—H⋯N hydrogen bonds, with each partially occupied water mol­ecule connected via an O—H⋯O hydrogen bond. C—H⋯O inter­actions are also present.

(E)-N'-(Furan-2-ylmethyl-ene)-4-(quinolin-8-yl-oxy)butanohydrazide

In the title mol­ecule, C₁₈H₁₇N₃O₃, the dihedral angle between the mean planes of the furan ring and the quinoline group is 77.4 (2)°. In the crystal structure, inter­molecular N—H⋯N hydrogen bonds link the mol­ecules into centrosymmetric dimers.