Zinc and Cadmium Complexes of Pyridinemethanol Carboxylates: Metal Carboxylate Zwitterions and Metal–Organic Frameworks

Abstract

The heterofunctional lactone furo [3,4-b]pyridin-5(7H)-one (L 1 ) undergoes a coordination-induced ring-opening reaction with Zn(NO 3 ) 2 · 6H 2 O to yield the zwitterionic [Zn(L 1 ') 2 (H 2 O) 2 ] (1, L 1 ' = 2-(hydroxymethyl)nicotinate) with an uncoordinated carboxylate. The same reaction with Cd(NO 3 ) 2 · 4H 2 O provides a twodimensional (2D) network of [Cd(L 1 ') 2 ] n (3) with the carboxylates coordinated to cadmium(II) propagating the assembly. The corresponding reactions of Zn(NO 3 ) 2 · 6H 2 O and Cd(NO 3 ) 2 · 4H 2 O with 2-(hydroxymethyl)isonicotinic acid (HL 2 ) generated zwitter-ionic [Zn(L 2 ) 2 (H 2 O) 2 ] (2) and a 2D network [Cd(L 2 ) 2 ] n ·nDMF (4, DMF = N,N'-dimethylformamide), respectively. Complexes 1-4 are weakly emissive, giving ligand-centered emissions at 409 nm (1), 412/436 nm (2), 404 nm (3), and 412/436 nm (4) in CHCl 3 solutions upon excitation at 330 nm. This work points to the potential of using 'hidden' functionalities widely found in small organic molecules and natural products for the construction of coordination complexes with new functionality and potential applications. Cd(NO 3 ) 2 ·4H 2 O (15.5 mg, 0.05 mmol) and L 1 (13.5 mg, 0.1 mmol) were added to a Pyrex glass tube (10 cm in length and 0.5 cm in diameter) followed by DMF/H 2 O (1 mL/2 mL). The tube was sealed and heated in an oven at 120°C for three days and gradually cooled to ambient temperature at a rate of 5°C min À 1 . The colourless crystals formed were filtered, washed with DMF and dried under vacuum. Yield: (8.1 mg, 39 % based on Cd). Anal. Calcd. (%) for C 14 H 12 CdN 2 O 6 : C 40. 36, H 2.90, N 6.72; found: C 40.78, H 2.91, N 6.93. Cd(NO 3 ) 2 · 4H 2 O (31 mg, 0.1 mmol) and ethyl 2-(hydroxymethyl) isonicotinate (the precursor of HL 2 , 36 mg, 0.2 mmol) were ChemPlusChem Full Papers in DMF/H 2 O (4 mL/4 mL) and heated at 125°C for 72 h in a DURAN glass bottle. The light-yellow crystals formed were filtered and washed with DMF. Yield: (25.0 mg, 51 % based on Cd). Anal.

On the Single-Crystal Structure of Tenofovir Alafenamide Mono-Fumarate: A Metastable Phase Featuring a Mixture of Co-Crystal and Salt

“…In sharp contrast, in the deprotonated and conjugated form of the carboxylate, the two C-O distances are 1.239(4) Å and 1.277(4) Å , which are close values. The large discrepancy in the bond distances within the carboxylate of the acid as well as the similar distances in the carboxylate in deprotonated form are similar to zwitterionic and hemizwitterionic coordination complexes such as trans- [ [26][27][28]. The structure refinement results for the possible location of the protons, combined with the similarity and differences in the in C-O bond distances in the carboxylate, provide convincing evidence that the fumarate is present in both its acid (75%) and deprotonated (25%) forms, endorsing 2 as a mixture of both co-crystal and salt.…”

“…•H 2 O, and [CuCl(hmnH 2 )(hmnH)] (iso-hmnH = 2-(hydroxymethyl) isonicotinate; hmnH = 2-(hydroxymethyl)nicotinate) [26][27][28]. The structure refinement results for the possible location of the protons, combined with the similarity and differences in the in C-O bond distances in the carboxylate, provide convincing evidence that the fumarate is present in both its acid (75%) and deprotonated (25%) forms, endorsing 2 as a mixture of both co-crystal and salt.…”

Impact of L-Pyroglutamic Acid on the Solubility of Puerarin: Preparation, Solid-State Characterization and Physicochemical Evaluation of Puerarin-L-Pyroglutamic Acid Co-Crystal

“…The various properties of an API (such as solubility, dissolution rate, bioavailability, permeability) could successfully be modified by forming pharmaceutical co-crystals. [17,18]. In this work, we successfully enhanced the physicochemical properties of PUE, such as solubility and time-dependent dissolution rate, via recrystallization technique by producing a novel crystalline phase co-crystal with bio-compactable co-former PG.…”

Connectivity Replication of Neutral Eu3+- and Tb3+-Based Metal–Organic Frameworks (MOFs) from Anionic Cd2+-Based MOF Crystallites

“…Moreover, this seeded growth could be facilitated by the usually high and flexible coordination numbers of lanthanides. 47,48,51,52 We introduced Eu(NO 3 ) 3 •6H 2 O and H 3 BTB in the presence of a small amount of MOF 1 crystals at room temperature. Colorless needle-shaped single crystals of 2 formed after 2 weeks.…”

“…This assertion was based on reports that Cd 2+ and Ln 3+ often form simple mononuclear or dinuclear secondary building units (SBUs) − and so topologically identical MOF growth seeded by 1 would not require significant geometry distortion. Moreover, this seeded growth could be facilitated by the usually high and flexible coordination numbers of lanthanides. ,,, …”