Four Hydrogen Bonds − DDAA, DADA, DAAD and ADDA Hydrogen Bond Motifs

Abstract

Receptor molecules containing four hydrogen-bond acceptor or donor sites based on aminopyridines, aminonaphthyridines and urea subunits have been synthesized and their association has been investigated. DDAA (13a−c) and DADA (18a−b) arrays may form homodimers, while DAAD (24a−d) with ADDA (25a−b) may form heterodimers. While most parent heterocycles were only slightly soluble in standard organic solvents, substitution was able to enhance the solubility in most cases. The naphthyridine 24d, bearing a substituMultiple hydrogen bonds can be found in many recognition processes, both in enzymes and in the genetic code. [1] Correct binding by two or three parallel [2] or antiparallel hydrogen bonds is the key feature of the genetic code, which uses substituted purines and pyrimidines for the recognition and the storage of genetic information. [3] The number of hydrogen bonds involved in a recognition event has two important influences on the quality of this process: (i) the more hydrogen bonds are involved in a recognition, the tighter the binding usually becomes, [4Ϫ7] and (ii) more hydrogen bonds can convey more information.A hydrogen bond between a hydrogen-bond donor (D) and a hydrogen-bond acceptor (A) possesses a direction. Therefore, with two hydrogen bonds, two different pairs, formed from three different molecules, are possible: a heterodimer in which a DD unit binds AA, and a homodimer made of two DA molecules. Addition of one more hydrogen bond results in three possible dimers formed by six different units: DDD·AAA, DDA·AAD and DAD·ADA. With four hydrogen bonds, ten different molecules and six different dimers are possible (see Figure 1).In addition to the stronger binding due to the four hydrogen bonds in these dimers, more information can be stored [ ‡] Multiple hydrogen bonds, 3. Part 2 Ref. [33] [a]

Polyurea–Urethane Supramolecular Thermo-Reversible Networks

“…Actually these results indicate that zigzag conformation is predominant for the various PU while folded intramolecular interaction is predominant for PU Bi (Figure ). Equivalent results were also reported in literature for systems with more than four hydrogen bond moieties. − …”

Polyurea–Urethane Supramolecular Thermo-Reversible Networks

“…Actually these results indicate that zigzag conformation is predominant for the various PU while folded intramolecular interaction is predominant for PU Bi (Figure ). Equivalent results were also reported in literature for systems with more than four hydrogen bond moieties. − …”

Synthesis of 10-Substituted Pyrido[2,3-b][1,8]naphthyridin-5(10H)-ones (Anthyridin-5(10H)-ones) Based on the Reaction of Bis(2-chloropyridin-3-yl)methanones with Primary Amines

“…When compound (1) and two equivalents of one of the primary amines were heated at 80 ˚C without using any solvents, substitution of an arylamino or an alkylamino group with one of the two chloro groups of 1 proceeded cleanly to afford the corresponding (2-aminopyridin-3-yl)(2-chloropyridin-3-yl)methanone derivatives (2). The progress of the substitution reaction could be monitored by TLC analyses on silica gel.…”

Association ofN-(Pyridin-2-yl),N′-substituted Ureas with 2-Amino-1,8-naphthyridines and Benzoates: NMR and Quantum Chemical Studies of the Substituent Effect on Complexation

“…Thus, the dimers of 1 – 4 are held together by two NH···O hydrogen bonds as depicted in Chart , which is in agreement with Etter’s rules. Similar dimers have been described before in the solid state ,,,,− and have been studied as compounds capable of interaction by four hydrogen bonds. , The single-crystal structure also shows the existence of two intermolecular NH···O interactions and an overall R 2 2 (8) motif (Figure ). The R 2 2 (8) refers to an eight-membered (8) ring ( R ) stabilized by two hydrogen bond acceptors ( 2 ) and two donors ( 2 ) as shown in Chart .…”

“…In general, CIS values are higher for amides than for amines. The association constants are lower than in other triply hydrogen-bonded complexes ,, due to the stabilization of the Z , E , Z isomer of ureas 1 – 4 by intramolecular hydrogen bonds. The conformational change in ureas caused by triple intermolecular hydrogen bonding (Chart ) is realized almost independently from R 2 and R 3 , showing that all ureas studied fit the triple AAD hydrogen bonding motif of 2-amino-1,8-naphthyridines.…”

Polyurea–Urethane Supramolecular Thermo-Reversible Networks

“…Actually these results indicate that zigzag conformation is predominant for the various PU while folded intramolecular interaction is predominant for PU Bi (Figure ). Equivalent results were also reported in literature for systems with more than four hydrogen bond moieties. − …”

Synthesis of 10-Substituted Pyrido[2,3-b][1,8]naphthyridin-5(10H)-ones (Anthyridin-5(10H)-ones) Based on the Reaction of Bis(2-chloropyridin-3-yl)methanones with Primary Amines

“…When compound (1) and two equivalents of one of the primary amines were heated at 80 ˚C without using any solvents, substitution of an arylamino or an alkylamino group with one of the two chloro groups of 1 proceeded cleanly to afford the corresponding (2-aminopyridin-3-yl)(2-chloropyridin-3-yl)methanone derivatives (2). The progress of the substitution reaction could be monitored by TLC analyses on silica gel.…”

Association ofN-(Pyridin-2-yl),N′-substituted Ureas with 2-Amino-1,8-naphthyridines and Benzoates: NMR and Quantum Chemical Studies of the Substituent Effect on Complexation

“…Thus, the dimers of 1 – 4 are held together by two NH···O hydrogen bonds as depicted in Chart , which is in agreement with Etter’s rules. Similar dimers have been described before in the solid state ,,,,− and have been studied as compounds capable of interaction by four hydrogen bonds. , The single-crystal structure also shows the existence of two intermolecular NH···O interactions and an overall R 2 2 (8) motif (Figure ). The R 2 2 (8) refers to an eight-membered (8) ring ( R ) stabilized by two hydrogen bond acceptors ( 2 ) and two donors ( 2 ) as shown in Chart .…”

“…In general, CIS values are higher for amides than for amines. The association constants are lower than in other triply hydrogen-bonded complexes ,, due to the stabilization of the Z , E , Z isomer of ureas 1 – 4 by intramolecular hydrogen bonds. The conformational change in ureas caused by triple intermolecular hydrogen bonding (Chart ) is realized almost independently from R 2 and R 3 , showing that all ureas studied fit the triple AAD hydrogen bonding motif of 2-amino-1,8-naphthyridines.…”

Polyurea–Urethane Supramolecular Thermo-Reversible Networks

“…Actually these results indicate that zigzag conformation is predominant for the various PU while folded intramolecular interaction is predominant for PU Bi (Figure ). Equivalent results were also reported in literature for systems with more than four hydrogen bond moieties. − …”

Synthesis of 10-Substituted Pyrido[2,3-b][1,8]naphthyridin-5(10H)-ones (Anthyridin-5(10H)-ones) Based on the Reaction of Bis(2-chloropyridin-3-yl)methanones with Primary Amines

“…When compound (1) and two equivalents of one of the primary amines were heated at 80 ˚C without using any solvents, substitution of an arylamino or an alkylamino group with one of the two chloro groups of 1 proceeded cleanly to afford the corresponding (2-aminopyridin-3-yl)(2-chloropyridin-3-yl)methanone derivatives (2). The progress of the substitution reaction could be monitored by TLC analyses on silica gel.…”

Association ofN-(Pyridin-2-yl),N′-substituted Ureas with 2-Amino-1,8-naphthyridines and Benzoates: NMR and Quantum Chemical Studies of the Substituent Effect on Complexation

“…Thus, the dimers of 1 – 4 are held together by two NH···O hydrogen bonds as depicted in Chart , which is in agreement with Etter’s rules. Similar dimers have been described before in the solid state ,,,,− and have been studied as compounds capable of interaction by four hydrogen bonds. , The single-crystal structure also shows the existence of two intermolecular NH···O interactions and an overall R 2 2 (8) motif (Figure ). The R 2 2 (8) refers to an eight-membered (8) ring ( R ) stabilized by two hydrogen bond acceptors ( 2 ) and two donors ( 2 ) as shown in Chart .…”

“…In general, CIS values are higher for amides than for amines. The association constants are lower than in other triply hydrogen-bonded complexes ,, due to the stabilization of the Z , E , Z isomer of ureas 1 – 4 by intramolecular hydrogen bonds. The conformational change in ureas caused by triple intermolecular hydrogen bonding (Chart ) is realized almost independently from R 2 and R 3 , showing that all ureas studied fit the triple AAD hydrogen bonding motif of 2-amino-1,8-naphthyridines.…”