Efficient fluorescent recognition of ATP/GTP by a water-soluble bisquinolinium pyridine-2,6-dicarboxamide compound. Crystal structures, spectroscopic studies and interaction mode with DNA.

The new dicationic pyridine-2,6-dicarboxamide-based compound 1 bearing two N-alkylquinolinium units was synthesized, structurally determined by single-crystal X-ray diffraction, and studied in-depth as a fluorescent receptor for nucleotides and inorganic phosphorylated anions in pure water. The addition of nucleotides to 1 at pH = 7.0 quenches its blue emission with a selective affinity towards adenosine 5'-triphosphate (ATP) and guanosine 5'-tripohosphate (GTP) over other nucleotides such CTP, UTP, ADP, AMP, dicarboxylates and inorganic anions. On the basis of the spectroscopic tools (1H, 31P NMR, UV-vis, fluorescence), MS measurements and DFT calculations, receptor 1 binds ATP with high affinity (log K = 5.04) through the simultaneous formation of strong hydrogen bonds and π-π interactions between the adenosine fragment and quinolinium ring with binding energy calculated in 8.7 kcal mol-1. High affinity for ATP/GTP is attributed to the high acidity of amides and preorganized rigid structure of 1. Receptor 1 is an order of magnitude more selective for ATP than GTP. An efficient photoinduced electron transfer quenching mechanism with simultaneous receptor-ATP complexation in both the excited and ground states is proposed. Additionally, multiple spectroscopic studies and molecular dynamics simulations showed that 1 can intercalate into DNA base pairs.

Chemosensing of Guanosine Triphosphate Based on a Fluorescent Dinuclear Zn(II)-Dipicolylamine Complex in Water.

Guanosine triphosphate (GTP) is a key biomarker of multiple cellular processes and human diseases. The new fluorescent dinuclear complex [Zn2(L)(S)][OTf]4, 1 (asymmetric ligand, L = 5,8-Bis{[bis(2-pyridylmethyl)amino] methyl}quinoline, S = solvent, and OTf = triflate anion) was synthesized and studied in-depth as a chemosensor for nucleoside polyphosphates and inorganic anions in pure water. Additions at neutral pH of nucleoside triphosphates, guanosine diphosphate, guanosine monophosphate, and pyrophosphate (PPi) to 1 quench its blue emission (λem = 410 nm) with a pronounced selectivity toward GTP over other anions, including adenosine triphosphate (ATP), uridine triphosphate (UTP), and cytidine triphosphate (CTP). The efficient quenching response by the addition of GTP was observed in the presence of coexisting species in blood plasma and urine with a detection limit of 9.2 µmol L-1. GTP also shows much tighter binding to the receptor 1 on a submicromolar level. On the basis of multiple spectroscopic tools (1H, 31P NMR, UV-vis, and fluorescence) and DFT calculations, the binding mode is proposed through three-point recognition involving the simultaneous coordination of the N7 atom of the guanosine motif and two phosphate groups to the two Zn(II) atoms. Spectroscopic studies, MS-ESI, and DFT suggested that GTP bound to 1 in 1:1 and 2:2 models with high overall binding constants of log ß1 (1:1) = 6.05 ± 0.01 and log ß2 = 10.91 ± 0.03, respectively. The optical change and selectivity are attributed to the efficient binding of GTP to 1 by the combination of a strong electrostatic contribution and synergic effects of coordination bonds. Such GTP selectivity of an asymmetric metal-based receptor in water is still rare.

Hydrogen bonding capabilities of group 14 homologues of HCN and HNC.

This study is directed towards assessing hydrogen bond acceptor/donor capabilities of heavier group 14 homologues of HCN and HNC. A structural, energetic and topological study using ab initio (MP2, CCSD(T)), electrostatic potential (EP) and quantum theory of atoms in molecules (QTAIM) methodologies was carried out on HNX⋯HNX and HXN⋯HXN dimers and their respective monomers, where X = C, Si, Ge, Sn and Pb. The obtained results suggest the presence of weak hydrogen bonds in both kinds of complexes, and remarkably Ge and Sn act as unconventional hydrogen donors.