William S. Sheldrick

The coordination polymers [CuBr(1, 7‐phen‐κN7)] (1a), [CuI(1, 7‐phen)] (2a) and [(CuI)₂(1, 7‐phen‐κN7)] (2b) may be prepared by treatment of the appropriate copper(I) halide with 1, 7‐phenanthroline (1, 7‐phen) in acetonitrile. 1a exhibits staircase CuBr double chains, 2a novel quadruple CuI chains. Their thermal properties were investigated by DTA‐TG and temperature resolved powder X‐ray diffraction. On heating, both 1:1 compounds decompose to 2:1 polymers and then finally to CuBr or CuI. With 4, 7‐phenanthroline (4, 7‐phen), CuBr affords both 1:1 and 2:1 complexes (5a, 5b), CuI 1:1 , 2:1 and 3:1 complexes(6a, 6b, 6c) in acetonitrile at 20 °C. 5a and 6a display lamellar coordination networks, with the former containing zigzag CuBr single chains, the latter 4‐membered (CuI)₂ rings. A second 2:1 complex [(CuI)₂(4, 7‐phen‐μ‐N4, N7)] (6b′) with staircase CuI double chains can be obtained by reacting CuI with 4, 7‐phen in a sealed glass tube at 110 °C. Both 5a and 6a exhibit thermal decomposition pathways of the general type 1:1 → 2:1 → 3:1 → CuX, and novel CuX triple chains are proposed for the isostructural 3:1 polymers 5c and 6c. X‐ray structures are reported for complexes 1a, 2b, [(CuCN)₃(CH₃CN)(1, 7‐phen‐μ‐N1, N7)] (3c·CH₃CN), [CuSCN(1, 7‐phen‐κN7)] (4a), 5a, 6a and [CuCN(4, 7‐phen‐μ‐N4, N7)] (7a).

The DNA binding of cationic complexes of the type [(η⁶-arene)Ru(Aa)(dppz)] (CF₃SO₃)_n (arene = C₆H₆, Me₃C₆H₃, C₆Me₆; dppz = dipyrido[3,2-a:2′,3′-c]phenazine; n = 1, Aa = AcH₋₁cysOH 4–6; n = 2, Aa = AcmetOH 7–9; n = 3, Aa = H₂metOMe 10–12) containing S-coordinated amino acids (HcysOH = L-cysteine, HmetOH = L-methionine) has been studied by UV-vis titration and 2D-NOESY. Stable intercalative binding is indicated for these complexes by their steady decrease in absorbance at maxima between 350 and 390 nm on titration with CT DNA and the bathochromic shifts of these absorption maxima. Taking 4–12 and the analogous (η⁶-C₆Me₆)Ru^II complexes of the tripeptides HglyglycysOH (n =1, 13) and HglyglymetOH (n = 2, 15; HglyOH = glycine) into account, typical DNA binding constant (K_b) ranges can be established for (η⁶-arene)Ru^II complexes: 5.3 × 10⁴–1.6 × 10⁵ M⁻¹ for monocations, 6.3 × 10⁵–9.9 × 10⁵ M⁻¹ for dications and 1.6 × 10⁶–5.5 × 10⁶ M⁻¹ for trications. These K_b values clearly reflect a strengthening of electrostatic interactions with the negatively charged phosphodiester backbone of DNA as the total cation charge increases. A consistent trend to higher K_b values is also apparent for the coligand series C₆H₆ < Me₃C₆H₃ < C₆Me₆ with the relative increase being, in general, more pronounced for C₆H₆/Me₃C₆H₃ pairs. The strong electronic influence of the coligand on dppz intercalation is also reflected by marked increases ΔT_m of 18.2–18.5 °C in the CT DNA thermal denaturation temperature for di- and tri-cationic (η⁶-C₆Me₆)Ru^II complexes. Upfield ¹H NMR chemical shifts and characteristic NOE cross peaks for the dppz protons of the 1 ∶ 1 complex formed between 9 and d(GTCGAC)₂ are consistent with a side-on intercalation adjacent to T₂ from the major groove.

The pH- and time-dependent reaction of cis-[PtCl₂(NH₃)₂] with the methionine- and histidine-containing peptides H-Gly-Met-OH, H-Gly-Gly-Met-OH, Ac-His-Gly-Met-OH, and Ac-His-(Ala)₃-Met-OH at 313 K has been investigated by ion-pairing reverse phase HPLC and NMR spectroscopy. For equimolar solutions (c=0.8 mM, pH≈3 or 8.8), initial formation of the kinetically favored S-bound complex is followed by relatively rapid metallation of the neighboring methionine amide nitrogen N _M to afford a κ² N _M,S six-membered chelate. The strong trans effect of the methionine S then favors facile NH₃ substitution, leading to generation of tridentate complexes such as [Pt(H-Gly-MetH_–1-OH)-κ³ N _G,N _M,S )(NH₃)]⁺ or [Pt(H-Ac-His-GlyH_–1-MetH_–1-OH-κ³ N _G,N _M,S)(NH₃)]. In the case of H-Gly-Gly-Met-OH, this reaction is accompanied by loss of a second NH₃ ligand in alkaline solution to generate the tetradentate κ⁴ N _G1,N _G2,N _M,S species. In contrast, cleavage of the backbone C(O)-N bond to the second metallated amide nitrogen after t>100 h is common to the tridentate complexes of the tri- and pentapeptides at pH2 N3 _H,S macrochelate is formed throughout the whole range 2.5≤pH≤10 for Ac-His-Gly-Met-OH, it slowly decays (t=10–1000 h) to the thermodynamically more stable tridentate κ³ N _G,N _M,S complex. All major final products were separated and fully characterized by NMR and MS.

Technological interest in the design of multifunctional microporous materials has stimulated recent research into the development of mild solventothermal techniques for the construction of lamellar and framework Main Group chalcogenidometalates. Reaction pathways from elemental or metal chalcogenide sources can be influenced by a variety of often interdependent factors of which counter cation size and charge, solvent polarity, pH and temperature are of paramount importance. As reviewed in this article, the presence of predominant solution species such as cyclic tripyramidal M₃S₆ ³⁻ (M = As or Sb) or edge-bridged ditetrahedral Sn₂E₆ ⁴⁻ anions (E = S or Se) as molecular building units and their participation in columnar substructures is characteristic for M₂S₃- and SnE₂-based anionic networks. Hierarchical topological relationships between individual members of structural families of the type A_xM_yE_z (A = alkali metal or alkylammonium cation) can be established that provide a detailed insight into probable multiple-step cation-directed self-assembly mechanisms. These findings enable the development of rational guidelines for the employment of suitable counter cations in controlling the condensation of small solution species into chains, sheets or frameworks, whose cavities reflect the spatial requirements of the structure-directing agent.