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Zipped‐Up Chain‐Type Coordination Polymers: Unsymmetrical Amide‐Containing Ligands Inducing β‐Sheet or Helical Structures
Author(s) -
Uemura Kazuhiro,
Kumamoto Yuki,
Kitagawa Susumu
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800806
Subject(s) - isonicotinamide , amide , chemistry , crystallography , pyridine , stereochemistry , crystal structure , hydrogen bond , solvent , molecule , medicinal chemistry , organic chemistry
The crystal structures of thirteen Ag I coordination polymers involving py‐CONH‐(CH 2 ) n ‐py (py=pyridine; n =0, 1) derivatives were determined by means of single‐crystal X‐ray analyses. All of the compounds form one‐dimensional chains composed of Ag I atoms and bridging ligands with formulas {[Ag(py‐CONH‐(CH 2 ) n ‐py)][X]} n (X=PF 6 − , ClO 4 − , BF 4 − , and NO 3 − with solvent molecules). The unsymmetrical coordination environments around Ag I atoms induce direction in the chains, that is, ‐[NH‐(CH 2 ) n ‐py‐Ag‐py‐CO]‐, which resembles the alignment of amino acid chains in proteins. In compounds {[Ag(4‐pia)][X]} n ( 1 ⊃X; 4‐pia= N ‐(4‐pyridyl)isonicotinamide; X=PF 6 − , ClO 4 − , BF 4 − , and NO 3 − ), {[Ag(4‐pmia)][X]} n ( 2 ⊃X; 4‐pmia= N ‐(pyridin‐4‐ylmethyl)isonicotinamide; X=PF 6 − , ClO 4 − ⋅ H 2 O, and NO 3 − ⋅ H 2 O), and {[Ag(3‐pmia)][X]} n ( 3 ⊃X; 3‐pmia= N ‐(pyridin‐3‐ylmethyl)isonicotinamide; X=PF 6 − , ClO 4 − , BF 4 − , and NO 3 − ⋅ H 2 O), each chain is aligned parallel to neighboring chains, but adjacent chains run in the opposite direction. Particularly in {[Ag(3‐pmia)][PF 6 ]} n ( 3 ⊃PF 6 − ), {[Ag(3‐pmia)][ClO 4 ]} n ( 3 ⊃ClO 4 − ), and {[Ag(3‐pmia)][BF 4 ]} n ( 3 ⊃BF 4 − ), amide moieties of 3‐pmia ligands are complementarily hydrogen bonded to amide moieties in neighboring chains, as in the β‐sheet motif in proteins. On the other hand, in {[Ag(4‐pmna)][PF 6 ] ⋅ MeOH} n (4‐pmna= N ‐(pyridin‐4‐ylmethyl)nicotinamide), all chains in the crystal form left‐handed ( 4 a ⊃PF 6 − ⋅ MeOH) and right‐handed ( 4 b ⊃PF 6 − ⋅ MeOH) helical structures with a helical pitch of 28 Å. Heterogeneous anion exchanges proceed reversibly in 2 , but not in 3 , which provides information about the thermal stabilities of the crystals.