Rational Design of a Novel Intercalation System. Layer-Gap Control of Crystalline Coordination Polymers, {[Cu(CA)(H2O)m](G)}n (m = 2, G = 2,5-Dimethylpyrazine and Phenazine; m = 1, G = 1,2,3,4,6,7,8,9-Octahydrophenazine)

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Abstract
New copper(II) intercalation compounds, {[Cu(CA)(H2O)2](G)}n (H2CA = chloranilic acid; G = 2,5-dimethylpyrazine (dmpyz) (1a and 1b) and phenazine (phz) (2)) have been synthesized and characterized. 1a crystallizes in the triclinic space group P1̄, with a = 8.028(2) Å, b = 10.269(1) Å, c = 4.780(2) Å, α = 93.85(3)°, β = 101.01(2)°, γ = 90.04(3)°, and Z = 1. 1b crystallizes in the triclinic space group P1̄, with a = 8.010(1) Å, b = 10.117(1) Å, c = 5.162(1) Å, α = 94.40(1)°, β = 97.49(1)°, γ = 112.64(1)°, and Z = 1. 2 crystallizes in the triclinic space group P1̄, with a = 8.071(1) Å, b = 11.266(1) Å, c = 4.991(1) Å, α = 97.80(1)°, β = 99.58(1)°, γ = 83.02(1)°, and Z = 1. For all the compounds, the crystal structures consist of one dimensional [Cu(CA)(H2O)2]m chains and uncoordinated guest molecules (G). Each copper atom for 1a, 1b, and 2 displays a six-coordinate geometry with the two bis-chelating CA2- anions and water molecules, providing an infinite, nearly coplanar linear chains running along the a-direction. Theses chains are linked by hydrogen bonds between the coordinated water and the oxygen atoms of CA2- on the adjacent chain, forming extended layers, which spread out along the ac-plane. The guest molecules are intercalated in between the {[Cu(CA)(H2O)2]k}l layers, just like pillars, which are supported with N···H2O hydrogen bonding. The guest molecules are stacked each other with an interplanar distance of ca. 3.2 Å along the c-axis perpendicular to the [Cu(CA)(H2O)2]m chain. The EHMO band calculations of intercalated dmpyz and phz columns show an appreciable band dispersion of phz π (b2g and b3g) and dmpyz π (bg), indicative of the importance of planar π structure for the formation of the intercalated structure. The distances of O−H---N (guest molecules) fall within the range 2.74−2.80 Å, insensitive to the guest, whereas the interlayer distances increase in the order 9.25 Å (1b), 10.24 Å (1a), and 11.03 Å (2). The degree in lengthening the distance correlates well with the size of a molecule, indicative of the stability of the 2-D sheet structure and the flexibility of the sheet packing. The magnetic susceptibilities were measured from 2 to 300 K and analyzed by a one-dimensional Heisenberg-exchange model to yield J = −1.83 cm-1, g = 2.18 (1a), J = −0.39 cm-1, g = 2.14 (1b), and J = −1.84 cm-1, g = 2.18 (2). The absolute value of J is smaller than that value for [Cu(CA)]n, which has a planar ribbon structure suggesting that the magnetic orbital dx2-y2 is not parallel to the chloranilate plane. For comparison with phz another type of copper(II) coordination compound, {[Cu(CA)(H2O)](ohphz)}n (ohphz = 1,2,3,4,6,7,8,9-octahydrophenazine (7)) has also been obtained. 7 crystallizes in the orthorhombic space group Cmcm with a = 7.601(2) Å, b = 13.884(2) Å, c = 17.676(4) Å, and Z = 4. Nonplanar ohphz molecules are in between [Cu(CA)(H2O)2]m chains with the N···H2O hydrogen bonding in a fashion parallel to the chain direction. The copper atom shows a five-coordinate square-pyramidal configuration with two CA and one water molecule, thus affording no hydrogen bonding links between chains, dissimilar to 1a, 1b, and 2. The magnetic susceptibilities yield J = −10.93 cm-1 and g = 2.00, comparable to that of the four-coordinate [Cu(CA)]n. On this basis both hydrogen bonding and stack capability of a guest molecule is responsible for building the unique intercalated structure such as is seen in 1a, 1b, and 2.

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