Tải bản đầy đủ - 0 (trang)
D. Copper Polymers Assembled by Dithioether and Polythioether Ligands Bearing Heteroelements in the Spacer Unit

D. Copper Polymers Assembled by Dithioether and Polythioether Ligands Bearing Heteroelements in the Spacer Unit

Tải bản đầy đủ - 0trang

Luminescent Copper Polymers Assembled by Thioether Ligands



C



O



C



O



N

CuCN



O



139



C



O



N



Cu



S



S



O



N



Cu



C



S



S



O



Cu



C



C

O



O



O



O



N



N

Cu



S



S



O



N



Cu



S



S



O



Cu



Square-grid-type 2D polymer 37

O



O

Double-stranded 1D polymer 37'



S



O



S

O



O



O



O



L37

S



S



O



S



CuI



I



I



I

Cu



S



O



Cu



Cu



Cu

I



I

Cu



O



S



O



S



I

Cu



O



S



O



O



S



O



SCHEME 17



O



O



CuI



S



S



MeCN/CH2Cl2



[Cu2I2(L38)2] ϩ [Cu4I4(L38)2]'

2D polymer 38



polymer 38'



nonemissive



emissive



L38

SCHEME 18



consist of 3D networks, in which Cu(μ2I)2Cu rhomboids with short Cu?Cu

distances of 2.654(7) A˚ coordinate the functionalized calixarene ligands in an

exocyclic manner. In the orthorhombic crystals, the 3D networks of composition [Cu4I4(L39)] 39u are assembled through closed cubane-like Cu4I4 clusters,

which act as three-dimensional connecting nodes bound to four different tetrakisthioether ligands. The individual Cu?Cu distances within the cubes are

variable and range from 2.607 to 2.995 A˚, the mean value being 2.77 A˚ (at 173 K).



140



Luminescent Oligomeric and Polymeric Copper Coordination



Whereas 39 is not emissive at room temperature, despite the short Cu?Cu

distances, compound 39u exhibits in the solid state a bright orange-yellow emission at 531 nm after excitation at 350 nm, arising from a CC-excited state with

mixed XMCT character. Figure 50 shows also that a second high-energy band is

present with a weaker maximum at B420 nm.

A similar mixed oxaÀthia macrocycle incorporating a rigid horseshoeshaped aromatic moiety, 1,11,21-trioxa-8,14-dithia[2,9,2]paracyclophane, L40,

has been synthesized and reacted with copper iodide in MeCN solution

(Scheme 19).160 Its polymeric copper iodide complex [Cu4I4(L40)2] 40 crystallizes,

in a 2:1 metal: to ligand ratio, as an 1D infinite array of cubane-like units consisting of four copper atoms, four μ3-iodine atoms, and four sulfur atoms, stemming from four different macrocycles. The CuÀCu distances are about 2.731 A˚.

Unfortunately, the photophysics of this compound have not been studied.

(a)



(b)

531 nm

200



S



S



O



O



O O



Intensity (a.u.)



O



150



420 nm



100



S



S

O



50

400



450



500

550

Wavelength (nm)



600



650



FIGURE 50. (a) Illustration of the calix[4]bis(thiacrown-5) ligand L39. (b) Solid-state

emission spectrum of 3D polymer 39u (298 K) incorporating closed Cu4I4 clusters as

connecting nodes. (Modified from Ref. 159.)



S



S



O



S

CuI



O



L40



O



S



MeCN



I



Cu



Cu

I

Cu

S

I



I



Cu

S



1D [Cu4I4{␮-L40}2]n



SCHEME 19



40



Luminescent Copper Polymers Assembled by Thioether Ligands



141



A nice example of a temperature-dependent self-assembly process providing

three different networks, stemming from the reaction of CuI with the calix[4]bisdithiacrown-6 ligand L41 is presented in Schemes 20 and 21.161 Mixing L41

with CuI in a 1:2 ratio at room temperature yields the nonemissive 3D polymer of

formula [(Cu3I3)L41(CH3CN)]n 41, in which the thiacrown ethers macrocycles are

connected via three-runged ladder-type units of type Cu3(μ3-I)(μ-I)2. Two Cu3I3

building blocks bridge two L41 macrocycles via CuÀS bonds to yield a 2D layer;

then the adjacent 2D layers are bridged via CuÀS bonds to form the 3D framework. As shown in Figure 51, the Cu2 atom of the inorganic unit of 41 is tetrahedrally coordinated by three I atoms and one MeCN molecule; within this first

example of such a coordination sphere, the Cu?Cu separations of 2.921 and

2.851 A˚ are significantly longer than the van der Waals radii (2.80 A˚).161

Upon removal of the coordinated MeCN solvent molecule by heating

at 175 C, the initial solvent-coordinated polymer 41 undergoes a unique

O



I



O



S



S



O



O



O



Cu



I



I



S

O



Cu

O



O



S



S



O



O



Cu



O



S



O



Cu



I



Cu



I

Cu



O



O



O



S



S

O



I



O



41', 3D-linked with Cu3I3 units (emissive; on)



O



S



S



O



O



175 ؇C



-CH3CN



NCCH3

O

O



I



O



O

S



S



CuI



S



S



O



O



Cu



Cu

I



O



I

Cu



O



S



S

O



O



O



O



298 K

O



L41



O



O



O



S



S



MeCN/CH2Cl2

S



S



Cu

O



O



I



I

Cu



Cu

O



O



I



NCCH3



41, 3D-linked with Cu3I3(CH3CN) units (nonemissive; off )



SCHEME 20



142



Luminescent Oligomeric and Polymeric Copper Coordination



I



O



Cu



Cu



Cu



I



I



O



O



O



S



S



S



S

O



O



O



O



I



I

Cu



Cu



O



S



S



O



O



I



O



L41

O



CuI



O



O



O



O



I



263 K

MeCN/CH2Cl2



I



Cu

O



S



S



S



S

O



I



O



I

Cu

Cu

Cu



I



O



Cu



Cu



O

S



S



I

O



O



41'', 3D-linked with Cu2I2 and Cu4I4 units

emissive



SCHEME 21



FIGURE 51. Crystallographic modification of the Cu3(μ3-I)(μ-I)2 core units after

single-crystal to single-crystal 41-41u transformation induced by evaporation of

coordinated MeCN.



single-crystal to single-crystal transformation to yield the desolvated polymer 41u

(Scheme 20). This elimination of MeCN was confirmed by a TGA study.

Although the overall structure of 41u is similar to that of 41, a marked change of

metric parameters of the Cu3(μ3-I)(μ-I)2 units was crystallographically evidenced.

Loss of MeCN causes a flattening of the Cu3I3 unit and contraction of the bond

lengths around the central Cu2 atom to 2.729 and 2.685 A˚, respectively.

As consequence of this cuprophilic interaction, desolvated polymer 41u

shows photoluminescence behavior. The authors attribute the observation of

bright yellow emission at 420 nm after excitation at 320 nm to an CC-excited

state with mixed XMCT character; the term solvato-photoluminescence was

coined for the offÀon behavior caused by the 41-41u transformation.161

It is interesting that the reaction of L41 in dichloromethane/MeCN with

two equivalents of CuI at -10 C afforded crystals of a 3D polymeric product of

formula [(Cu2I2)(L41)2(Cu4I4)]n 41v (Scheme 21). X-ray analysis revealed that

41v incorporates both cubane-type Cu4I4 and rhomboid-type Cu2I2 units linked



Luminescent Copper Polymers Assembled by Thioether Ligands



143



alternately by L41 ligands. Apart from our compound 2 (Fig. 3), material 41v is

a unique example of such a CuX complex; all other CuX complexes reported so

far are linked by only a single type of CuX cluster. Polymer 41v also exhibits an

intense orange emission (531 nm) in the solid state arising from the Cu4I4

cubane units.

The Lee group also prepared three CuI coordination polymers using the

calix[4]-bis monothiacrown ligand L42. If CuI in MeCN solution is reacted

with L42 in a 3:1 metal to ligand ratio, the colorless 1D polymer [(Cu4I4)

(CH3CN)2L42]n 42 is obtained. In this material, each L42 molecule is linked

to two closed cubane-type Cu4I4 units through its thioether functions

(Scheme 22). Two remaining copper(I) sites are ligated by MeCN molecules.

Within the Cu4I4 cluster, the Cu-Cu distances vary (at 293 K) between 2.6652

(10) and 2.7892(8) A˚. Upon excitation at 365 nm, polymer 42 exhibits at room

temperature a bright yellow emission at 567 nm, attributed to CC-excited state

with mixed iodide-to-metal charge transfer.162 According TGA and DSC

analysis, polymer 42 looses successively the Cu-bound MeCN molecules after

heating at 150 C to yield the compound 42u. If a microcrystalline sample of this

acetonitrile-free compound 42u, which displays an emission maximum around

600 nm, is exposed to MeCN, a reversible recoordination of acetonitrile occurs

to give back 42, as confirmed by TGA and XRPD analysis (Scheme 22). As

42', 1D-linked (red; emissive)

؊ MeCN

heat



CuI



NCCH3

CH3CN

Cu

I

I

Cu

I

Cu

Cu

I



؉ MeCN



O



O

O

O



S



O



O



O



O



S



O



S

O



O



O



42, 1D-linked with Cu4I4(CH3CN)2 unit (yellow; emissive)

O O

O



O



L42



O



I



S

CuI / KI



Cu

I



I

Cu

I



O

O



Cu



S



I

Cu



O



K

O



O

O



K



S



O



I



42", 1D-linked with Cu4I62؊ unit (nonemissive)



SCHEME 22



144



Luminescent Oligomeric and Polymeric Copper Coordination



noticed in the case of the 41-41u transformation, a photoluminescence

switching behavior can be induced by removal of coordinated solvent.

Noteworthy also is the reaction between L42 and CuI in the presence of KI.

The crystal structure determination reveals the formation of hitherto unknown

exocyclic Cu4I622 clusters, which are linked by L42 to generate a polymeric 1D

array of composition [K2(Cu4I6)L42]n 42v. Within the crown ether cavities of L42,

two potassium ions are trapped in an endocyclic manner. Also, upon inclusion of

the K1 ions the crown ring shrinks leading to opening of opposite aromatic rings

in the host calixarene unit, a rare behavior for this class of compound.162

A luminescent 3D staircase coordination polymer of composition

[Cu3I3(L43)]n 43, based on planar Cu3I3 units, has been constructed by the reaction

of CuI with 1,4-bis[(cyclohexylthio)acetyl)piperazine L43 (Scheme 23).163 The

linear arrangement of the inorganic staircase ribbon is depicted in Figure 52.

Within the Cu3I3 units, the CuÀCu distances of 2.6175(9) A˚ are very short. In

contrast, the loose Cu?Cu contact of 3.1686(17) A˚ with the adjacent units indicates very weak cuprophilic interactions between the Cu3I3 building blocks. The

L43 ligand links the staircase chains in a 3D manner by bonding through

the thioether functions. Upon excitation at 325 nm, a broad emission with a

maximum at 546 nm, which is temperature independent, is displayed. The authors

assign the luminescence to a combination of XMCT and d-s transitions due to

the short metal-metal interactions within the Cu3I3 motif.

Kim’s group also prepared the 1,12-diphenyl-5,8-dioxa-2,11-dithidodecane

ligand L44 and reacted it with CuI.164 Contrary to our failure to assemble a

network with 1,8 bis(phenylthio)octane, L44 containing eight spacer units

between the sulfur atoms allowed the construction of a 2D square-grid-type

coordination polymer 44. This finding may be rationalized by the enhanced

basicity of -S-benzyl vs. -S-phenyl (Scheme 23).

The 2D network contains cubane-like Cu4I4 clusters located at the nodes

of the square grid and coordinated to four L44 ligands by CuÀS bonds forming



O

S



N



O



S

N

S



L43



O



S



L44



O



CuI



MeCN



CuI



3D [Cu3I3(L43)] 43 luminescent



SCHEME 23



MeCN



2D [Cu4I4(L44)] 44 luminescent



Luminescent Copper Polymers Assembled by Thioether Ligands



145



FIGURE 52. Projection of the inorganic 1D ribbon of the 3D polymer [Cu3I3(L43)] 43.



a layer structure. The layers are stacked with an ABAB sequence. The short

Cu?Cu distances of 2.778(2) and 2.802 A˚ are certainly responsible for the

strongly emissive character of this material. At 298 K, a broad emission band

with a maximum at 565 nm (λexcit 5 325 nm) is observed. Like in the case of

our structurally related compound 16, coordination polymer 44 exhibits

luminescence thermochromism. The maximum is red shifted to B604 nm at

7 K; in addition, a second weaker high-energy band emerges at B452 nm.

The same group also explored the reactivity of the two asymmetric

dithioether ligands with cyclohexyl (L45) and phenyl (L46) end groups toward

CuI.164 Reaction of 2 (cyclohexylmethylthio)-1-thiomorpholinoethanone L45

with copper(I) iodide afforded a 1D channel-type coordination polymer

[Cu4I4(L45)2]n 45, interconnected by cubane-like tetranuclear Cu4I4 cluster

units (Scheme 24). The mean Cu?Cu distance within the cluster cubes

amounts to 2.749 A˚ at 173 K.

Upon irradiation by UV light (λexcit 5 325 nm), the metallopolymer 45

exhibits a bright green emission (λem 5 525 nm) in the solid state. In contrast, a

non-emissive 2D brick-wall type coordination polymer of composition

[Cu2I2(L46)2]n 46 with rhomboid dinuclear CuÀI2ÀCu nodes resulted from the

reaction of 2-(benzylthio)-1-thiomorpholinoethanone L46 with CuI. Compared

to the short Cu?Cu distance in 45, the metal?metal contacts within the

rhomboids of 46 are much longer and reach 2.856(2) A˚.

Another example of a single-crystal to single-crystal transformation has

been observed in metallopolymers 47, 47u, and 47’u, obtained by reaction of

dithioether 2-(cyclohexythio)-1-thiomorpholinoethanone L47 with copper(I)

iodide.165 The nonemissive 1D polymer [Cu2I2(L47)2]n 47 is formed in the selfassembly process after mixing CuI and ligand L47 in a 1:1 ratio using MeCN

as solvent (Scheme 25). Within the monodimensional loop chain, rhomboid

Cu2I2 units with loose metal?metal contacts of 2.98 A˚ act as connecting

nodes. Treatment of L47 with an excess of CuI in a MeCN/Et2O mixture as

reaction medium produces however the luminescent polymer [Cu4I4(L47)2]n

47u, in which the thioether groups of L47 span tetranuclear Cu4I4 clusters

giving rise to a 2D network. 2D polymer 47u is also formed in MeCN solution

by adding an excess of CuI to 1D polymer 47. Alternatively, compound 47

can be converted to compound 47’ by heating a sample of 47 at 180 C in the

solid state.



146



Luminescent Oligomeric and Polymeric Copper Coordination

S



S



N



O



O

S



N



I

S



L45



Cu



MeCN



I

Cu



I

O



S



N



Cu



Cu



I



Cu



I



S



S



S



N



S



I

Cu



I



O



Cu

I



Cu



O



N



1D polymer 45



S



luminescent



CuI

Cu

I



I

O



Cu

O

S

L46

MeCN



S



S

S



N



N



Cu



S



N

S



O



Cu

I



I



I



O



Cu

S



N

N



I

Cu



S



S



S

Cu



O

I



I

Cu



2D polymer 46

nonemissive



SCHEME 24



The nonnegligible influence of the polarity of the solvent mixture in this

reaction is demonstrated by the observation that conducting the reaction of

CuI with L47 in MeCN/nhexane lead to the formation of a solvated 1D

polymer with composition [Cu4I4(L47)2(MeCN)(C6H14)]n 47uu. This luminescent material incorporating closed-cubane Cu4(μ3-I)4 clusters undergoes a

crystal to crystal transformation upon heating to 180 C in the solid state with

extrusion of MeCN and n-hexane affording 2D material 47u.

An important finding of Kim’s group is the experimental correlation of

the metric structural parameters within the Cu4I4 clusters of 47u and 47uu and

their luminescence thermochromism in function of the temperature. Table 2

presents the single-crystal X-ray data concerning the Cu?Cu distances of

these two compounds, which have been recorded at four different temperatures. Analysis of these values reveals that the shorter Cu?Cu bond lengths do

not contract much with decreasing temperature; however, the longer Cu?Cu

contacts are much more affected and shrink below the sum of the Van der

Waals radii.166

In other words, the bonding character increases, thus lowering the energy

level, accompanied by a lowering of the energy difference between the excited



Luminescent Copper Polymers Assembled by Thioether Ligands



147



O

N



S



S



Cu



Cu

I



CuI



I



I

Cu



CH3CN



I

Cu



S

S



N



1D [Cu2I2(L47)2]n 47

(nonemissive)



O

S

N



Excess CuI at 70 ЊC

in CH3CN or

heating at 180 ЊC in

solid state



Excess L45

in CH3CN



O

S



Cu



L47



Cu



CH3CN/Et2O



Cu



S



I Cu

Cu



I



Excess CuI



O



I



N



I



I



S



I

I

Cu S

Cu

Cu



N



I



O



S

O



I



N

S



Cu



I



S



Cu

Cu

I



I



I



Cu



Cu

Cu I



N

S

O



S



Cu



I



I

Cu



2D [Cu4I4(L47)2]n 47'

(emissive)



SCHEME 25



TABLE 2. Cu?Cu distances (A˚) in 47u and 47uu recorded at four different temperatures



298 K



223 K



173 K



123 K



47u

Cu1?Cu3

Cu1?Cu2

Cu3?Cu4

Cu2?Cu3

Cu1?Cu4

Cu2?Cu4



2.833(2)

2.789(2)

2.755(2)

2.740(2)

2.625(2)

2.631(2)



2.8052(17)

2.7642(17)

2.7446(17)

2.7267(17)

2.6213(18)

2.6169(17)



2.7878(13)

2.7513(13)

2.7400(13)

2.7182(13)

2.6221(14)

2.6107(13)



2.7733(10)

2.7403(11)

2.7410(10)

2.7111(11)

2.6292(11)

2.6079(11)



47uu

Cu2?Cu4

Cu1?Cu2

Cu3?Cu4

Cu1?Cu4

Cu2?Cu3

Cu1?Cu3



2.814(3)

2.815(3)

2.760(3)

2.748(3)

2.736(3)

2.672(3)



2.7930(13)

2.7871(13)

2.7469(13)

2.7321(12)

2.7234(13)

2.6594(12)



2.7809(11)

2.7752(11)

2.7344(11)

2.7175(11)

2.7091(11)

2.6501(10)



2.7713(10)

2.7652(10)

2.7235(10)

2.7030(10)

2.6981(10)

2.6432(10)



148



Luminescent Oligomeric and Polymeric Copper Coordination

200



298 K



538 nm



Emission Intensity



77 K

150



526 nm



100



50



0

400



450



500

Wavelength (nm)



550



600



FIGURE 53. Solid-state emission spectra of 1D polymer [Cu4I4(L47)2(MeCN)

(C6H14)]n 47u, recorded at 298 K and 77 K after excitation at 286 nm. (Modified from

Ref. 166.)



states and the ground state. (Note that according to theoretical studies, the

Cu?Cu interactions in the excited state have LUMO character and are

bonding).67 The CuÀS bond lengths remain nearly constant within this temperature range.

In line with the variation of the Cu?Cu interaction in function of the

temperature, the emission maximum in the solid-state luminescence spectrum

(λexcit 5 350 nm) of 47u appears considerably red shifted when the temperature

is decreased from 298 K (538 nm) to 77 K (599 nm). The red shift is less

pronounced in the case of compound 47uu; Figure 53 reveals that the lowtemperature spectrum is somewhat less broadened than that recorded at room

temperature.

We and Rabinovich’s group have reported on the synthesis of siliconbased bidentate and tridentate thioethers R4-nSi(CH2SR)n (n 5 2, 3; R 5 Me,

Ph) and characterized a wide variety of complexes in which they act as either

terminal or bridging ligands.167À169 For example, reaction of CuX with the

tridentate thioether ligand MeSi(CH2SMe)3 yielded the 1D coordination

polymers [Cu3{MeSi(CH2SMe)3}2X3] (X 5 Cl, Br).170 Our group reacted the

dithioether ligand Ph2Si(CH2SPh2) L48 with one equivalent of CuI, leading to

the dinuclear 0D system [CuI{Ph2Si(CH2SPh)2}]2 48 (Scheme 26). As corroborated by an X-ray diffraction study, the L48 dithioether coordinates in a

chelating manner at the Cu center, which is attached to a second moiety by two

μ2-I atoms. The Cu?Cu interaction in the resulting rhomboid motif is close to

the sum of Van der Waals radii and amounts to 2.7964(6) A˚. This complex

exhibits a luminescence of only medium intensity; the emission spectrum shown



Luminescent Copper Polymers Assembled by Thioether Ligands

Ph

SPh



Ph

Si



Si



Ph



MeCN



SPh



Ph

I



S



Ph



CuI



S



Cu



Ph



Ph



Cu

I



S



L48



149



Ph



Si

Ph



S

Ph



48



Ph

PhS



SPh



HgBr2



SPh



Toluene



Ge

PhS



Br



S



PhS

Ge

PhS



Hg

S

Br



L49



Ph

n

MeCN



CuI

Ph

S



Ph

I



S



PhS



Ph



PhS

Ge



S



PhS

Ge

PhS



Cu



Cu

I



S

Ph



Ph

S



PhS

Ge



49



S

Ph



PhS

n



SCHEME 26



in Figure 54 displays two maxima at 417 and 435 nm after excitation at 360 nm.

Overall, the emission spectrum of dinuclear compound 48 is very similar to that

of 2D polymer 14 (Fig. 23).

We have demonstrated in a collaborative work that tetrathioether ligands

of type Si(CH2SR)4 (R 5 Me, Ph) may be used as assembling ligands to construct monodimensional coordination polymers of type [{Si(CH2SR)4}HgBr2]n

upon reaction with HgBr2.171 Continuing our studies on multidentate thioethers, we set out to evaluate and compare the coordinative properties of the

tetrakisthioether ligand Ge(CH2SPh)4 L49 with those of its silicon analogue Si

(CH2SPh)4.172

The reaction of CuI with 0.5 Eq of L49 in MeCN gave colorless crystals

of [(CuI)2{Ge(CH2SPh)4}]n 49 (Scheme 26). This 2D coordination polymer

is constructed by dinuclear Cu2(μ2-I)2 units, which are linked by the



Tài liệu bạn tìm kiếm đã sẵn sàng tải về

D. Copper Polymers Assembled by Dithioether and Polythioether Ligands Bearing Heteroelements in the Spacer Unit

Tải bản đầy đủ ngay(0 tr)

×