From Short-Bite Ligand Assembled Ribbons to Nanosized
Networks in Cu(I) Coordination Polymers Built Upon Bis(benzylthio)alkanes
(BzS(CH2)nSBz; n = 1–9)
posted on 2020-03-05, 20:12authored byAdrien Schlachter, Antony Lapprand, Daniel Fortin, Carsten Strohmann, Pierre D. Harvey, Michael Knorr
With the objective
to establish a correlation between the spacer distance and halide
dependence on the structural features of coordination polymers (CPs)
assembled by the reaction between CuX salts (X = Cl, Br, I) and dithioether
ligands BzS(CH2)nSBz (n = 1–9; Bz = benzyl), a series of 26 compounds have
been prepared and structurally investigated. A particular attention
has been devoted to the design of networks with extremely long and
flexible methylene spacer units between the SBz donor sites. Under
identical conditions, CuI and CuBr react with BzSCH2Bz
(L1) affording respectively the one-dimensional (1D)
CPs {Cu(μ2-I)2Cu}(μ-L1)2]n (CP1) and {Cu(μ2-Br)2Cu}(μ-L1)2] (CP2), which incorporate Cu(μ2-X)2Cu rhomboids as secondary building units (SBUs).
The hitherto unknown architecture of two-dimensional (2D) layers obtained
with CuCl (CP3) differs from that of CP1 and CP2, which bear inorganic −Cl–Cu–Cl–Cu–Cl–
chains interconnected through bridging L1 ligands, thus
forming a 2D architecture. The crystallographic characterization of
a 1D CP obtained by reacting CuI with 1,3-bis(benzylthio)propane (L2) reveals that [{Cu(μ2-I)2Cu}(μ-L2)2]n (CP4) contains conventional Cu2I2 rhomboids as
SBUs. In contrast, unusual isostructural CPs [{Cu(μ2-X)}(μ2-L2)]n (CP5) and (CP6) are obtained
with CuX when X = Br and Cl, respectively, in which the isolated Cu
atoms are bridged by a single μ2-Br or μ2-Cl ion giving rise to infinite [Cu(μ2-X)Cu]n ribbons. The crystal structure of the strongly
luminescent three-dimensional (3D) polymer [{Cu4(μ3-I)3(μ4-I)(μ-L3)1.5]n (CP7)
issued from reacting 2 equiv of CuI with BzS(CH2)4SBz (L3) has been redetermined. CP7 features
unusual [(Cu4I3)(μ4-I)]n arrays securing the 3D connectivity. In contrast,
mixing CuI with an excess of L3 provides the nonemissive
material [{Cu(μ2-I)2Cu}(μ-L3)2]n (CP8). Treatment of CuBr and CuCl with L3 leads to [{Cu(μ2-Br)2Cu}(μ-L3)2]n (CP9) and the 0D complex [{Cu(μ2-Cl)2Cu}(μ-L3)2] (D1), respectively. The crystallographic particularity
for CP9 is the coexistence of two topological isomers
within the unit cell. The first one, CP9-1D, consists of simple 1D ribbons running along the a axis of the unit cell. The second topological isomer, CP9-2D, also consists of [Cu(μ2-Br)2Cu] SBUs, but these are interconnected in a 2D manner forming
2D sheets placed perpendicular to the 1D ribbons. Four 2D CPs, namely,
[{Cu4(μ3-I)4}(μ-L4)2]n (CP10), [{Cu(μ2-I)2Cu}(μ-L4)2]n (CP11), [{Cu(μ2-Br)2Cu}(μ-L4)2]n (CP12),
and [{Cu(μ2-Cl)2Cu}(μ-L4)2]n (CP13), stem from the self-assembly process of CuX with BzS(CH2)6SBz (L4). A similar series of 2D materials
comprising [{Cu4(μ3-I)4}(μ-L5)2]n (CP14), [{Cu(μ2-I)2Cu}(μ-L5)2]n (CP15), [{Cu(μ2-Br)2Cu}(μ-L5)2]n (CP16),
and [{Cu(μ2-Cl)2Cu}(μ-L5)2]n (CP17) result from the coordination of BzS(CH2)7SBz (L5) on CuX. Ligation of CuX with the long-chain
ligand BzS(CH2)8SBz (L6) allows
for the X-ray characterization of the luminescent 2D [{Cu4(μ3-I)4}(μ-L6)2]n (CP18) and the
isostructural 1D series [{Cu(μ2-X)2Cu}(μ-L6)2]nCP19 (X = I), CP20 (X = Br) and CP21(X = Cl).
Noteworthy, BzS(CH2)9SBz (L7) bearing
a very flexible nine-atom chain generated the crystalline materials
2D [{Cu4(μ3-I)4}(μ-L7)2]n (CP22) and the isostructural 1D series [{Cu(μ2-X)2Cu}(μ-L6)2]nCP23 (X = I), CP24 (X = Br),
and CP25 (X = Cl), featuring nanometric separations between
the cubane- or rhomboid-SBUs. This comparative study reveals that
the outcome of the reaction of CuX with the shorter ligands BzS(CH2)nSBz (n = 1–4)
is not predictable. However, with more flexible spacer chains BzS(CH2)nSBz (n = 6–9),
a clear structural pattern can be established. Using a 1:1 CuX-to-ligand
ratio, [{Cu(μ2-X)2Cu}(μ-L4–7)2] CPs are always formed, irrespectively
of L4–L7. Employing a 2:1 CuX-to-ligand
ratio, only CuI is able to form networks incorporating Cu4(μ3-I)4 clusters as SBUs. All attempts
to construct polynuclear cluster using CuBr and CuCl failed. The materials
have been furthermore analyzed by powder X-ray diffraction, Raman
spectroscopy, and thermogravimetric analysis, and the photophysical
properties of the emissive materials have been studied.