2-Fold interpenetration via ligand-induced alternating perpendicular helical channel motifs. Structure of an acentric diamondoid silver(I) coordination polymer† Tae Hwan Noh, a Youn Jung Choi, a Yoon Kyong Ryu, a Young-A Lee b and Ok-Sang Jung * a Received 18th March 2009, Accepted 24th June 2009 First published as an Advance Article on the web 23rd July 2009 DOI: 10.1039/b905296h The reaction of AgPF 6 in methanol with 1,3-dibromo-2,2-bis[(isonicotinoyloxy)methyl]propane (L) in dichloromethane affords an acentric diamondoid 3D silver(I) coordination polymer, [Ag(L) 2 ] n (PF 6 ) n with 2-fold interpenetration with alternating perpendicular ‘‘right-handed’’ and ‘‘left-handed’’ helical channel motifs induced by the bent ligand. Introduction Molecular materials with helical motifs have practical applica- tions in multidisciplinary areas such as templating precursors, 1 memory devices, 2 biomimetic chemistry, 3,4 chiral chemistry, 5 DNA, 6 and structural biology. 7 Control of such motifs has by now advanced to the point where the process can be addressed. 8 Formation of desirable helical or helical-like metal complexes seems to be strongly dependent on subtleties such as the angle, flexibility, and length of the spacer ligand. 9,10 Significant progress has been made in the functional helical metal complexes by self- assembly of metal ions with designed organic tectonics. The skewed conformer-tectonic ligand with nonrigid interannular dihedral angles is a key tectonic element of a rational strategy. 9 However, the construction of a new skeleton is often serendipi- tous given the coexistence of subtle factors such as p–p stack- ings, specific noncovalent interactions, and hydrogen bonds. 11–17 Various organic pyridyl ligands have been used as molecular building blocks. 18 Among such, (iso)nicotinoyl-containing ligands specifically possessing characteristic properties such as a potential multidentate, an sp 2 angle around C]O, malleable length, conformational nonrigidity, and manageable solubility have generated interesting metal complexes. 19–22 In the present study, 1,3-dibromo-2,2-bis[(isonicotinoylox-y)- methyl]propane (L) was prepared as a new spacer ligand. Silver(I) ion was employed as an angular directional unit of tetrahedral geometry. 22–26 We here describe a new 3 dimensional (3D) coordination polymers, [Ag(L) 2 ] n (PF 6 ) n , that is, interpene- tration of ligand-induced perpendicular ‘‘right-handed’’ and ‘‘left-handed’’ helical channel motifs. A variety of inter- penetrating coordination polymeric structures have been synthesized and received considerable attention, 27–31 even though the present metal complex is not an isolated helical structure. Experimental General remarks All chemicals were purchased from Aldrich and used without further purification. Infrared spectra were obtained on a Nicolet 380 FT-IR spectrophotometer with samples prepared as KBr pellets. 1 H and 13 C NMR spectra were recorded on a Varian Mercury Plus 300. Elemental analyses were performed on crys- talline samples using a Vario-EL III at Pusan center, KBSI. Thermal analysis was performed under a nitrogen atmosphere at a scan rate of 10  C min 1 with Labsys TGA-DSC 1600. Synthesis of 1,3-dibromo-2,2-bis[(isonicotinoyloxy)methyl]-propane (L) To a stirred mixture of isonicotinoyl chloride hydrochloride (21.36 g, 0.12 mol) in chloroform (150 mL) at room temperature was added pyridine (19.41 mL, 0.24 mol). Subsequently, 2,2- bis(bromomethyl)-1,3-propanediol (13.1 g, 0.05 mol) was added to the reaction solution, and the mixture was refluxed for 3 h. The chloroform layer was washed successively with 0.5 N NaOH solution and cold H 2 O. The chloroform layer was dried (MgSO 4 ) and filtered. After removal of the solvents, 1,3- dibromo-2,2-bis[(isonicotinoyloxy)methyl]propane (L) was obtained as viscous liquid. Excess hexane was added to the chloroform solution, and left at 5  C, affording white solids in a 75% yield. Anal. Calc. for C 17 H 16 N 2 O 4 Br 2 : C, 43.25; H, 3.42; N, 5.93. Found: C, 43.10; H, 3.30; N, 5.85. d H (300 MHz; CDCl 3 ; Me 4 Si) 8.59 (2H, d, J ¼ 6 Hz), 7.62 (2H, d, J ¼ 6 Hz), 4.41 (2H, s), 3.56 (2H, s). d C (75 MHz; CDCl 3 ; Me 4 Si) 163.72, 150.22, 135.84, 122.20, 64.22, 42.38, 32.99. IR (KBr/cm 1 ): 1740 (s, CO). a Department of Chemistry, Pusan National University, Pusan, 609-735, Republic of Korea. E-mail: oksjung@pusan.ac.kr; Fax: +82 51 516 3522; Tel: +82 51 510 2591 b Department of Chemistry, Chonbuk National University, Jeonju, 561-756, Republic of Korea. E-mail: ylee@chonbuk.ac.kr; Tel: + 82 63 207 3347 † CCDC reference number 720473. For crystallographic data in CIF or other electronic format see DOI: 10.1039/b905296h This journal is ª The Royal Society of Chemistry 2009 CrystEngComm, 2009, 11, 2371–2374 | 2371 PAPER www.rsc.org/crystengcomm | CrystEngComm