Systematic synthesis, isolation, and photophysical properties of linear-shaped Re(I) oligomers and polymers with 2-20 units

Published on Web 10/11/2008

Systematic Synthesis, Isolation, and Photophysical Properties

of Linear-Shaped Re(I) Oligomers and Polymers with

2-20 Units

Youhei Yamamoto,^†,‡Shuhei Sawa,^†Yusuke Funada,^†Tatsuki Morimoto,^†

Magnus Falkenstro¨m,^§Hiroshi Miyasaka,^§Sayaka Shishido,^|Tomoji Ozeki,^|

Kazuhide Koike, and Osamu Ishitani*^,†,‡

Department of Chemistry and Department of Chemistry and Materials Science, Graduate School

of Science and Engineering, Tokyo Institute of Technology, 2-12-1-E1-9 O-okayama, Meguro-ku,

Tokyo 152-8551, Japan, SORST, Japan Science and Technology Agency (JST), Japan, DiVision

of Frontier Materials Science, Graduate School of Engineering Science, and Center for

Quantum Science and Technology under Extreme Conditions, Osaka UniVersity, Toyonaka,

Osaka 560-8531, Japan, and National Institute of AdVanced Industrial Science and Technology,

16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan

Received June 12, 2008; E-mail: ishitani@chem.titech.ac.jp

Abstract: Systematic synthesis routes have been developed for the linear-shaped rhenium(I) oligomers

and polymers bridged with bidentate phosphorus ligands, [Re(N^N)(CO)₃-PP-{Re(N^N)(CO)₂-PP-}_n-

Re(N^N)(CO)₃](PF₆)_n+2(N^N ) diimine, PP ) bidentate phosphine, n ) 0-18). These were isolated by

size exclusion chromatography (SEC) and identiﬁed by ¹H NMR, IR, electrospray ionization Fourier transform

mass spectrometry, analytical SEC, and elemental analysis. Crystal structures of [Re(bpy)(CO)₃-

Ph₂PCtCPPh₂-Re(bpy)(CO)₃](PF₆)₂, [Re(bpy)(CO)₃-Ph₂PCtCPPh₂-Re(bpy)(CO)₂-Ph₂PCtCPPh₂-Re-

(bpy)(CO)₃](PF₆)₃and [Re(bpy)(CO)₃-Ph₂PC₂H₄PPh₂-{Re(bpy)(CO)₂Ph₂PC₂H₄PPh₂-}_nRe(bpy)(CO)₃](PF₆)_n+2

(bpy ) 2,2′-bipyridine, n ) 1, 2) were obtained, showing that they have interligand π-π interaction between

the bpy ligand and the phenyl groups on the phosphorus ligand. All of the oligomers and polymers

synthesized were emissive at room temperature in solution. For the dimers, broad emission was observed

with a maximum at 523-545 nm, from the ³MLCT excited-state of the tricarbonyl complex unit,

[Re(N^N)(CO)₃-PP-]. Emission from the longer oligomers and polymers with g3 Re(I) units was observed

at wavelengths 50-60 nm longer than those of the corresponding dimers. This fact and the emission decay

results clearly show that energy transfer from the edge unit to the interior unit occurs with a rate constant

of (0.9 × 10⁸)-(2.5 × 10⁸) s^-1. The efﬁcient energy transfer and the smaller exclusive volume of the

longer Re(I) polymers indicated intermolecular aggregation for these polymers in an MeCN solution.

Introduction

(1) organic main polymer chain derived by addition of metal

complexes as pendant groups, such as polystyrene connected

Rod-like polymers constructed of photofunction transition

metal complexes, having the ability to show photoinduced

energy and electron transfer, are of great interest because of

their potential for application in light-harvesting and light-

emitting devices and molecular-scale photonic wires.¹Such

transition metal complex polymers fall into three categories:

with Ru(II) and Os(II) polypyridyl complexes;^2,3(2) π-conju-

gated heteroaromatic polymers with diimine parts in a main

chain which coordinate to Ru(II) and/or Os(II) polypyridyl

complexes, such as poly (2,2′-bipyridine-5,5′-diyl) coordinated

to [Ru(bpy)₂]^{2+ 4-6}

and (3) metal ions incorporated into the

;

main chain of a polymer.^7-10Diverse examples of the metal

complex polymers in categories (1) and (2) have been synthe-

^†Department of Chemistry, Graduate School of Science and Engineering,

Tokyo Institute of Technology.

^‡SORST/JST.

(2) (a) Friesen, D. A.; Kajita, T.; Danielson, E.; Meyer, T. J. Inorg. Chem.

1998, 37, 2756–2762. (b) Dupray, L. M.; Devenney, M.; Striplin,

D. R.; Meyer, T. J. J. Am. Chem. Soc. 1997, 119, 10243–10244. (c)

Jones, W. E.; Baxter, S. M.; Strouse, G. F.; Meyer, T. J. J. Am. Chem.

Soc. 1993, 115, 1363–7373.

^§Division of Frontier Materials Science, Graduate School of Engineering

Science and Center for Quantum Science and Technology under Extreme

Conditions, Osaka University.

^|Department of Chemistry and Materials Science, Graduate School of

Science and Engineering, Tokyo Institute of Technology.

National Institute of Advanced Industrial Science and Technology.

(1) For reviews, see: (a) BalzaniV.; Moggi, L.; Scandola, F. In Supramo-

lecular Photochemistry; Balzani, V., Ed.; D. Reidel: Dordrecht, 1987;

pp 1-28. (b) Lehn, J.-M. Supramolecular Chemistry - Concepts and

PerspectiVes; VCH: Weinheim, 1995. (c) Sauvage, J. P.; Collin, J. P.;

Chambron, J. C.; Guillerez, S.; Coudret, C.; Balzani, V.; Barigelletti,

F.; De Cola, L.; Flamigni, L. Chem. ReV. 1994, 94, 993–1019. (d)

Huynh, M. H. V.; Meyer, T. J. Chem. ReV. 2007, 107, 5004–5064.

(3) Serin, J.; Schultze, X.; Adronov, A.; Frechet, J. M. J. Macromolecules

2002, 35, 5396–5404.

(4) (a) Harriman, A.; Khatry, A.; Ziessel, R. Res. Chem. Intermed. 2007,

33, 49–62. (b) Harriman, A.; Rostron, S. A.; Khatyr, A.; Ziessel, R.

Faraday Discuss. 2006, 131, 377–391. (c) Harriman, A.; Ziessel, R.

Coord. Chem. ReV. 1998, 171, 331–339. (d) Goeb, S.; DeNicola, A.;

Ziessel, R. J. Organomet. Chem. 2005, 70, 6802–6808.

(5) Connors, P. J.; Tzalis, D.; Dunnick, A. L.; Tor, Y. Inorg. Chem. 1998,

37, 1121–1123.

9

10.1021/ja8044579 CCC: $40.75

2008 American Chemical Society

J. AM. CHEM. SOC. 2008, 130, 14659–14674 14659

A R T I C L E S

Yamamoto et al.

sized, and their photophysical properties have been studied in

depth. In category (3), however, only two series of transition

metal oligomers which can emit in solution at ambient temper-

ature have been reported, even though they should have unique

properties because of the contribution of the d orbitals in the

transition metal ions to the main polymer chain. One series

comprises Pt(II) and Au(I) alkynyl polymers, such as trans-

[M(PR₃)₂(-CtC-R-CtC-)₂]_n(M ) Au or Pt, R ) none or

aromatic spacer), which emit from a metal-perturbed singlet and

triplet intraligand π-π* excited states.^11-13The other series

comprises triads constructed with one Os(II) bis-terpyridine and

two Ru(II) complexes, where two 2,2′:6′,2′′-terpyridine ligands

are connected to each other at the 4′ position with a spacer such

as p-phenylene.¹⁴Although they emit from the Os(II) unit, the

lifetime of the triplet excited state is much shorter than that of

the corresponding tris-bipyridine type complex due to a less

octahedral geometry of the surrounding ligands. Bis-terpyridine

connected with alkyne is a possible bridge ligand, since the

corresponding Ru(II) and Os(II) complexes can emit strongly

even in solution. However, most reported Ru(II) and Os(II)

complexes with such bridge ligands have been diad;¹⁵no longer

oligomer has yet been reported.

reduction.^20-22The Re(I) diimine complexes have also been

used as an “L-shaped” building block for supramolecules such

as molecular triangles and squares,^23,24because various diimines

and ligands, which are located in the cis position to each other,

may be introduced. Unfortunately, the photochemical and

thermal stabilities of the three carbonyl ligands on the Re(I)

diimine complexes seriously limit the synthesis of “linear”

multinuclear Re(I) complexes in which the bridge ligands are

coordinated in the trans positions of the central Re(I). Only

two linear-shaped trinuclear Re(I) complexes [{Re(bpy)-

(CO)₃(en)}₂Re(bpy)(CO)₂]³⁺(bpy ) 2,2′-bipyridine; en )

trans-1,2-bis(diphenylphosphino)ethylene) had been reported²⁵

prior to our preliminary communication.^26aWe have found a

novel photochemical ligand substitution reaction of fac-

[Re(LL)(CO)₃(PR₃)]⁺, as shown in eq 1.²⁷Since only the CO

ligand in the position trans to the phosphorus ligand is

substituted in this type of photochemical reaction, this discovery

provides a new synthesis method for a series of trans-substituted

Re(I) mononuclear complexes, namely cis,trans-[Re(LL)-

(CO)₂(PR₃)(Y)]⁺.^27aPhotochemical ligand substitution can be

also applied to a Re(I) dimer connected with a bridge ligand

such as 1,2-bis(diphenylphosphino)ethane (et) (eq 2),²⁶and we

have brieﬂy reported the synthesis of linear trinuclear and

tetranuclear Re(I) complexes in a previous communication.^26a

Below, we report general and systematic synthesis methods

for linear-shaped Re(I) oligomers and polymers (Chart 1). We

have successfully isolated polymers with up to 20 Re(I) units

and identiﬁed their precise structures by analytical methods such

as electrospray ionization Fourier transform mass spectrometry

(ESI FTMS), and size exclusion chromatography (SEC). They

can be dissolved in various organic solutions and emit strongly

at room temperature in solution. Details of their photophysical

properties are reported.

The rhenium(I) diimine complexes, fac-[Re(N^N)(CO)₃(X)]ⁿ⁺

(N^N ) diimine, X ) monodentate ligand), have been studied

for their unique photochemical properties, such as long lifetime,

high emission quantum yield,^16-19and photocatalysis for CO₂

(6) (a) Hayasida, N.; Yamamoto, T. Bull. Chem. Soc. Jpn. 1999, 72, 1153–

1162. (b) Yamamoto, T.; Maruyama, T.; Zhou, Z.-H.; Ito, T.; Fukuda,

T.; Yoneda, Y.; Begum, F.; Ikeda, T.; Sasaki, S.; Takezoe, H.; Fukuda,

A.; Kubotall, K. J. Am. Chem. Soc. 1994, 116, 4832–4845.

(7) Hissler, M.; El-ghayoury, A.; Harriman, A.; Ziessel, R. Angew. Chem.,

Int. Ed. 1998, 37, 1717–1720.

Results and Discussion

(8) (a) Knapp, R.; Kelch, S.; Schmelz, O.; Rehahn, M. Macromol. Symp.

2003, 204, 267–286. (b) Kelch, S.; Rehahn, M. Chem. Commun. 1999,

1123–1124. (c) Kelch, S.; Rehahn, M. Macromolecules 1999, 32,

5818–5828.

We used the synthetic strategy “complex as metal” and

“complex as ligand” proposed by Balzani²⁸for the synthesis of

linear-shaped oligo- and polynuclear Re(I) complexes. We

(9) Cho, T. J.; Mooreﬁeld, C. N.; Hwang, S.-H.; Wang, P.; God´ınez, L. A.;

Bustos, E.; Newkome, G. R. Eur. J. Org. Chem. 2006, 4193–4200.

(10) Hayashida, N.; Yamamoto, T. Bull. Chem. Soc. Jpn. 1999, 72, 1153–

1162.

(20) Hawecker, J.; Lehn, J.-M.; Ziessel, R. HelV. Chim. Acta 1986, 69,

1990–2012.

(11) (a) Yam, V. W. W.; Wong, K. M. C. In Molecular Wires; De Cola,

L., Ed.; Springer: Berlin, 2005; Vol. 257, pp 1-32. (b) Yam, V. W. W.;

Cheng, E. C. C.; In Photochemistry and Photophysics of Coordination

Compounds II; Balzani, V., Campagna, S., Eds.; Springer: Berlin,

2007; Vol. 281, pp 269-310. (c) Yam, V. W. W.; Lo, K. K. W.;

Wong, K. M. C. J. Organomet. Chem. 1999, 578, 3–30.

(12) Vicente, J.; Chicote, M. T.; Alvarez-Falcon, M. M.; Fox, M. A.;

Bautista, D. Organometallics 2003, 22, 4792–4797.

(21) Kurz, P.; Probst, B.; Spingler, B.; Alberto, R. Eur. J. Inorg. Chem.

2006, 15, 2966–2974.

(22) (a) Takeda, H.; Koike, K.; Inoue, H.; Ishitani, O. J. Am. Chem. Soc.

2008, 130, 2023–2031. (b) Koike, K.; Hori, H.; Ishizuka, M.; Westwell,

J. R.; Takeuchi, K.; Ibusuki, T.; Enjouji, K.; Konno, H.; Sakamoto,

K.; Ishitani, O. Organometallics 1997, 16, 5724–5729. (c) Hori, H.;

Ishihara, J.; Koike, K.; Takeuchi, K.; Ibusuki, T.; Ishitani, O. J.

Photochem. Photobiol., A 1999, 120, 119–124.

(13) (a) Yamamoto, Y.; Shiotsuka, M.; Onaka, S. J. Organomet. Chem.

2004, 689, 2905–2911. (b) Shiotsuka, M.; Yamamoto, Y.; Okuno, S.;

Kitou, M.; Nozaki, K.; Onaka, S. Chem. Commun. 2002, 590–591.

(14) (a) Harriman, A.; Ziessel, R. Coord. Chem. ReV. 1998, 171, 331–

339. (b) Barigelletti, F.; Flamigni, L.; Balzani, V.; Collin, J.-P.;

Sauvage, J.-P.; Sour, A.; Constable, E. C.; Thompson, A. M. W. C.

J. Am. Chem. Soc. 1994, 116, 7692–7699. (c) Benniston, A. C.;

Harriman, A.; Li, P.; Patel, P. V.; Sams, C. A. Chem. Eur. J. 2008,

14, 1710–1717.

(23) (a) O’Donnell, J. L.; Zuo, X.; Goshe, A. J.; Sarkisov, L.; Snurr, R. Q.;

Hupp, J. T.; Tiede, D. M. J. Am. Chem. Soc. 2007, 129, 1578–1585.

(b) Hupp, J. T. In Structure Bonding (Berlin); Alessio, E., Ed.;

Springer: Berlin, 2006; Vol. 121, pp 145-165.

(24) Barbaza´n, P.; Carballo, R.; Casas, J. S.; Garcia-Martinez, E.; Pereiras-

Gabia´n, G.; Sa´nchez, A.; Vazquez-Lo´pez, E. M. Inorg. Chem. 2006,

45, 7323–7330.

(25) Woessner, S. M.; Helms, J. B.; Lantzky, K. M.; Sullivan, B. P. Inorg.

Chem. 1999, 38, 4378–4379.

(15) (a) Harriman, A.; Hissler, M.; Khatyr, A; Ziessel, R. Eur. J. Inorg.

Chem. 2003, 955–959. (b) Grosshenny, V.; Harriman, A.; Ziessel, R.

Angew. Chem., Int. Ed. Engl. 1995, 34, 1100–1102.

(26) (a) Ishitani, O.; Kanai, K.; Yamada, Y.; Sakamoto, K. Chem. Commun.

2001, 1514–1515. (b) DelNegro, A. S.; Woessner, S. M.; Sullivan,

B. P.; Dattelbaum, D. M.; Schoonover, J. R. Inorg. Chem. 2001, 40,

5056–5057.

(16) Luong, J. C.; Nadjo, L.; Wrighton, M. S. J. Am. Chem. Soc. 1978,

100, 5790–5795.

(17) (a) Worl, L. A.; Strouse, F. S.; Younathan, J. N.; Baxter, S. M.; Meyer,

T. J. J. Am. Chem. Soc. 1990, 112, 7571–7578. (b) Caspar, J. V.;

Meyer, T. J. J. Phys. Chem. 1983, 87, 952–957. (c) Caspar, J. V.;

Meyer, T. J. J. Phys. Chem. 1983, 87, 952–957.

(27) (a) Koike, K.; Tanabe, J.; Toyama, S.; Tsubaki, H.; Sakamoto, K.;

Westwell, J. R.; Johnson, F. P. A.; Hori, H.; Saitoh, H.; Ishitani, O.

Inorg. Chem. 2000, 39, 2777–2783. (b) Koike, K.; Okoshi, N.; Hori,

H.; Takeuchi, K.; Ishitani, O.; Tsubaki, H.; Clark, I. P.; George, M. W.;

Johnson, F. P. A.; Turner, J. J. J. Am. Chem. Soc. 2002, 124, 11448–

11455.

(18) Schutte, E.; Helms, J. B.; Woessner, S. M.; Bowen, J.; Sullivan, B. P.

Inorg. Chem. 1998, 37, 2618–2619.

(19) Hori, H.; Koike, K.; Ishizuka, M.; Takeuchi, K.; Ibusuki, T.; Ishitani,

O. J. Organomet. Chem. 1997, 530, 169–176.

(28) Balzani, V.; Juris, A.; Venturi, M.; Campagna, S.; Serroni, S. Chem.

ReV. 1996, 96, 759–834.

9

14660 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Linear-Shaped Re(I) Oligomers and Polymers with 2-20 Units

A R T I C L E S

Chart 1. Structures and Abbreviations of Synthesized Oligo- and

Polynuclear Complexes, “Complex as Metal”, “Complex as

Ligand”, Diimine Ligands LL, and Bidentate Phosphorus Ligands X

(PPh₂-R-PPh₂)

prepared “complexes as metal”, where an easily replaceable

-

CF₃SO₃anion or a solvent molecule coordinates in the trans

position to a phosphorus bridge ligand, employing a photo-

chemical ligand substitution reaction of Re(I) monomers or

oligomers as described below. We prepared “complex as ligand”

having one or two η¹-type bidentatable phosphorus ligand(s),

of which one side coordinates to the central metal and the other

side is available for coordination to a further metal (Chart 1).

Coupling reactions or polymerization of these complexes gave

a series of linear-shaped oligo- and polynuclear Re(I) diimine

complexes. The relatively high solubility of these complexes

in polar organic solvents such as MeCN and MeOH allowed

isolation of polymers with up to 20 Re(I) units, using SEC.

As representative examples, synthesis of the linear-shaped

oligo- and polynuclear Re(I) complexes consisting of bis(diphe-

nylphosphino)acetylene (ac) as a bidentatable phosphorus ligand

and 2,2′-bipyridine (bpy) are described. The abbreviation

[ReNac]^N+is used for complexes with two Re(bpy)(CO)₃units

in both edges (N denotes the number of Re(I) units; ac indicates

that ac is the bridge ligand). “Complex as metal” and “complex

as ligand”, in which one or two CO ligand(s) in the edge unit(s)

are substituted with L′ (m ) 1, L′ ) CF₃SO₃^-; m ) 0, L′ )

CH₂Cl₂or MeCN) or ac, are respectively abbreviated as

[ReNac(L′)₁]^(N-m)+or [ReNac(L′)₂]^(N-2m)+(complexes as

coordinate with another metal center. A coupling reaction of

[Re2ac(η¹-ac)₁]²⁺with fac-Re(bpy)(CO)₃(CF₃SO₃) gives

[Re3ac]³⁺in a 82% isolated yield. For preparation of [Re4ac]⁴⁺

,

[Re2ac(CF₃SO₃)₁]⁺reacted with ac in a 2:1 molar ratio; the

isolated yield was 72%. Good yields were also obtained in the

synthesis of other tri- and tetranuclear complexes with various

bidentate phosphorus and diimine ligands, as summarized in

Table 1.

Photochemical Ligand Substitution Reactions of Re(I)

Oligomers. As described above, brief irradiation of a CH₂Cl₂

solution containing [Re2ac]²⁺(CF₃SO₃^-)₂selectively yields the

unsymmetrical dimer [Re2ac(CF₃SO₃)₁]⁺. Although [Re2-

ac(CF₃SO₃)₁]⁺was relatively stable against irradiation, because

of efﬁcient energy transfer from the tricarbonyl Re(I) unit to

another biscarbonyl Re(I) unit (eq 3), longer irradiation times

(such as for 15 h) caused further substitution of the CO

ligand(s) to give two products, [{Re(bpy)(CO)₂(CF₃SO₃)}₂(ac)]

([Re2ac(CF₃SO₃)₂]) and [Re(bpy)(CO)₂(CF₃SO₃)(ac)Re(bpy)-

(CO)(CF₃SO₃)(L′)] (L′ should be CH₂Cl₂as solvent), where

[Re2ac(CF₃SO₃)₁]⁺still remained in the solution (Figure S1

in Supporting Information).

metal), and [ReNac(η¹-ac)_{1 or 2}^N+(complex as ligand) (Chart

]

1).

Synthesis of Di-, Tri-, and Tetranuclear Re(I) Complexes.

The dinuclear complex [Re(bpy)(CO)₃(ac)Re(bpy)(CO)₃]²⁺

([Re2ac]²⁺) was obtained in high yield by thermal reaction of

fac-Re(bpy)(CO)₃(CF₃SO₃) with a 0.5 equiv of ac. It was then

used as a precursor for the synthesis of oligomers and polymers.

Scheme 1 summarizes the synthesis of the trinuclear complex

[Re(bpy)(CO)₃(ac)Re(bpy)(CO)₂(ac)Re(bpy)(CO)₃]³⁺([Re3-

ac]³⁺) and the tetranuclear complex [Re(bpy)(CO)₃(ac)-

{Re(bpy)(CO)₂(ac)}₂Re(bpy)(CO)₃]⁴⁺([Re4ac]⁴⁺). A dichlo-

romethane solution containing CF₃SO₃^-salts of [Re2ac]²⁺was

irradiated under an Ar atmosphere for 30 min, giving

[Re(bpy)(CO)₃(ac)Re(bpy)(CO)₂(CF₃SO₃)]⁺([Re2ac(CF₃-

SO₃)₁]⁺) where one carbonyl ligand in the position trans to the

ac ligand was substituted with CF₃SO₃^-. Thermal reaction of

[Re2ac(CF₃SO₃)₁]⁺with excess ac in CH₂Cl₂led to substitution

[Re*(bpy)(CO)₃(ac)Re(bpy)(CO)₂(CF₃SO₃)]⁺f

[Re(bpy)(CO)₃(ac)Re*(bpy)(CO)₂(CF₃SO₃)]⁺(3)

The photochemical behavior of [Re3ac]³⁺and [Re4ac]⁴⁺was

different from that of [Re2ac]²⁺. Even after 45 min irradiation,

much [Re4ac]⁴⁺remained in the solution, while the disubstituted

product [Re4ac(CF₃SO₃)₂]²⁺was produced accompanied by

-

of the CF₃SO₃ligand by ac, to give [Re(bpy)(CO)₃-

(ac)Re(bpy)(CO)₂(η¹-ac)]²⁺([Re2ac(η¹-ac)₁]²⁺), where ac in

the edge (η¹-ac) works as a monodentate ligand and can

9

J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008 14661

A R T I C L E S

Yamamoto et al.

Scheme 1. Synthesis of Linear-Shaped Tri- and Tetranuclear Rhenium(I) Complexes^a

^aReagents and reaction conditions: (i) hV (>330 nm) in CH₂Cl₂for 30 min; (ii) excess ac in CH₂Cl₂at room temperature for 1 day, then at 40 °C for

1 day; (iii) fac-Re(bpy)(CO)₃(CF₃SO₃) in CH₂Cl₂at room temperature for 1 day, then at 40 °C for 1 day; (iv) ac (0.5 equiv) in CH₂Cl₂at room temperature

for 1 day, then at 40 °C for 1 day.

[Re3ac]³⁺or [Re4ac]⁴⁺as starting complexes. The synthesis

Table 1. Isolated Yields of Linear-Shaped Di-, Tri-, and

Tetranuclear Complexes with Various Bidentate Phosphorus

is shown in Scheme 2. A dichloromethane solution containing

Ligands

-

CF₃SO₃salts of [Re3ac]³⁺was irradiated for 1 h to give a

mixture of [Re3ac(CF₃SO₃)₁]²⁺and [Re3ac(CF₃SO₃)₂]⁺, where

yield/%

LL )

X )

bpy

bu

dmb^bMeObpy^c

one or two carbonyl ligand(s) in one or both edge unit(s) are

substituted with CF₃SO₃^-. The mixture also contained the

starting complex [Re3ac]³⁺, but further irradiation gave a

complex with a monocarbonyl rhenium(I) unit in the edge,

[Re(bpy)(CO)₂(CF₃SO₃)(ac)Re(bpy)(CO)₂(ac)Re(bpy)(CO)-

complex^a

ac

et

pr

pe

he

en

ac

[Re2X]²⁺

[Re3X]³⁺

[Re4X]⁴⁺

94 95 92 93 92 93 94

82 63 70 81 57 59 62

72 75 60 68 60 63 85

90

64

75

91

41

81

(CF₃SO₃)₂], as byproduct. The ratio of [Re3ac(CF₃SO₃)₁]²⁺

,

-

^aIsolated as PF₆salts. ^b4,4′-Dimethy-2,2′-bipyridine. ^c4,4′-Dimethoxy-

[Re3ac(CF₃SO₃)₂]⁺, and [Re3ac]³⁺was approximately 3:1:5.

A thermal reaction of this mixture with [Re2ac(η¹-ac)₁]²⁺as

“complex as ligand” gave both [Re(bpy)(CO)₃(ac){Re(bpy)-

(CO)₂(ac)}₃Re(bpy)(CO)₃]⁵⁺([Re5ac]⁵⁺)and[Re(bpy)(CO)₃(ac)-

{Re(bpy)(CO)₂(ac)}₅Re(bpy)(CO)₃]⁷⁺([Re7ac]⁷⁺) in 32% and

2,2′-bipyridine.

[Re4ac(CF₃SO₃)₁]³⁺(Figure S2b in Supporting Information).

Four tetranuclear complexes, i.e., [Re4ac]⁴⁺

, [Re4ac-

(CF₃SO₃)₁]³⁺, [Re4ac(CF₃SO₃)₂]²⁺, and [Re4ac(CF₃SO₃)₃]⁺

coexisted in the solution after 1.5 h irradiation (Figure S2c in

Supporting Information). The trimer [Re3ac]³⁺had similar

photochemical reactivity to [Re4ac]⁴⁺. As described in the

“Emission” section, intramolecular energy transfer took place

from the excited edge Re(I) unit to the interior Re(I) unit, so

that the lifetime of the excited state of the edge unit in both

[Re3ac]³⁺and [Re4ac]⁴⁺was much shorter (∼10 ns) than that

of [Re2ac]²⁺. We have reported previously that photochemical

ligand substitution reaction of mononuclear Re(I) complexes

with a phosphorus ligand, fac-[Re(bpy)(CO)₃(PR₃)]⁺, proceeds

via the triplet metal-centered excited state (³ML), which is

thermally in equilibrium with the emissive and lowest excited

state, i.e. a triplet metal-to-ligand charge transfer excited state

(³MLCT). Since it is reasonable to suppose that the photochemi-

cal ligand substitution reaction of the multinuclear complexes

also proceeds via the same mechanism, the shorter excited

lifetime of the edge Re(I) unit in trimer and tetramer because

of the efﬁcient energy transfer explains why the efﬁciency of

the photochemical ligand substitution of [Re3ac]³⁺and

9% yields, respectively, along with 53% recovery of [Re3ac]³⁺

.

By a similar method, using [Re4ac]⁴⁺instead of [Re3ac]³⁺as

a precursor complex, hexa- and octanuclear complexes

[Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}_nRe(bpy)(CO)₃]⁽ⁿ⁺²⁾⁺(n

) 4, [Re6ac]⁶⁺; n ) 6, [Re8ac]⁸⁺) were synthesized in 23%

and 3% yields, respectively, with 43% recovery of [Re4ac]⁴⁺

.

The corresponding multinuclear Re(I) complexes with et as

bridge ligands were obtained by a similar method. The yields

were 37% for [Re(bpy)(CO)₃(et){Re(bpy)(CO)₂(et)}₃-

Re(bpy)(CO)₃]⁵⁺([Re5et]⁵⁺) and 5% for [Re(bpy)(CO)₃(et)-

{Re(bpy)(CO)₂(et)}₅Re(bpy)(CO)₃]⁷⁺([Re7et]⁷⁺), with 65%

recovery of the starting complex [Re3et]³⁺. These methods

should therefore be applicable to the synthesis of other

complexes connected by various bidentate phosphorus ligands.

We have developed another method for selective synthesis

of [Re5ac]⁵⁺in higher yield. A thermal reaction of fac-

Re(bpy)(CO)₃(CF₃SO₃) with excess ac in a THF solution gave

fac-[Re(bpy)(CO)₃(η¹-ac)]⁺. This solution was irradiated for 1

night, giving cis,trans-[Re(bpy)(CO)₂(η¹-ac)₂]⁺(eq 4). A ther-

mal reaction of cis,trans-[Re(bpy)(CO)₂(η¹-ac)₂]⁺with two

equivalents of [Re2ac(CF₃SO₃)₁]⁺in CH₂Cl₂gave [Re5ac]⁵⁺

in 66% yield (eq 5). Unfortunately, this method cannot be

[Re4ac]⁴⁺was much lower than that of [Re2ac]²⁺

.

Synthesis of Complexes with 5-8 Re(I) Units. Complexes

with 5-8 Re(I) units were synthesized using CF₃SO₃^-salts of

9

14662 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Linear-Shaped Re(I) Oligomers and Polymers with 2-20 Units

Scheme 2. Synthesis of Oligomers with 5 and 7 Re(I) Units^a

A R T I C L E S

^aReagents and reaction conditions: (i) hV (>330 nm) in CH₂Cl₂for 1 h; (ii) [Re2ac(η¹-ac)₁]²⁺in CH₂Cl₂at room temperature for 1 day, then at 40 °C

for 1 day.

Scheme 3. Synthesis of Linear-Shaped Re(I) Polymers^a

^aReagents and reaction conditions: (i) hV (>330 nm) in MeCN for 1 h; (ii) excess ac in acetone/THF (1:1) at room temperature for 1 day, then at 40 °C

for 1 day; (iii) in acetone/THF (1:1) at room temperature for 1 day, then at 40 °C for 2 days.

applied to synthesize pentanuclear complexes with other bi-

dentate phosphorus ligands, such as et, because irradiation of

these complexes gave mainly cis-[Re(bpy)(η²-et)(CO)₂]⁺even

in the presence of excess phosphorus ligand (eq 6).

at 40 °C for 2 days. Figure S3 in Supporting Information shows

a size exclusion chromatogram of the crude product. This result

clearly indicates the formation of various Re(I) polymers in

which the number of rhenium(I) units is a multiple of 5, such

as [Re10ac]¹⁰⁺, [Re15ac]¹⁵⁺, [Re20ac]²⁰⁺, and [Re25ac]²⁵⁺

.

Polymerization. We attempted the polymerization of Re(I)

complexes using [Re5ac]⁵⁺as a starting complex (Scheme 3),

because [Re5ac]⁵⁺can be synthesized in high yield by relatively

simple procedures, as described above. An acetonitrile solution

Some of the products, [Re10ac]¹⁰⁺

, , and

[Re15ac]¹⁵⁺

[Re20ac]²⁰⁺, were isolated using SEC as described below, in

yields of 16%, 6%, and 4%, respectively, with 50% recovery

of [Re5ac]⁵⁺. Polymers with more than 20 Re(I) units could

not be isolated, because of their low yields. By a similar method,

using [Re4ac]⁴⁺instead of [Re5ac]⁵⁺as a precursor complex,

[Re8ac]⁸⁺, [Re12ac]¹²⁺, and [Re16ac]¹⁶⁺were obtained in

yields of 19%, 14%, and 3%,respectively, with 55% recovery

-

containing the PF₆salts of [Re5ac]⁵⁺was irradiated for 1 h,

giving a mixture of [Re5ac(MeCN)₁]⁵⁺, [Re5ac(MeCN)₂]⁵⁺

,

and [Re5ac]⁵⁺. After evaporation of the solvent, one-half of

the residue reacted with excess ac in a mixed solution of acetone

and THF (1:1 v/v) under an Ar atmosphere, generating a mixture

of [Re5ac(η¹-ac)₁]⁵⁺and [Re5ac(η¹-ac)₂]⁵⁺. Both mixtures

which were “complexes as metals”, i.e., [Re5ac(MeCN)₁]⁵⁺

and [Re5ac(MeCN)₂]⁵⁺, and “complexes as ligands”, i.e.,

[Re5ac(η¹-ac)₁]⁵⁺and [Re5ac(η¹-ac)₂]⁵⁺, were dissolved in an

acetone/THF (1:1 v/v) mixed solution, and was a maintained

of [Re4ac]⁴⁺

.

Isolation and Identiﬁcation. We isolated the Re(I) oligomers

and polymers by SEC, using a hydrophilic column for gel

ﬁltration and a methanol/acetonitrile (1:1) mixed eluent contain-

9

J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008 14663

A R T I C L E S

Yamamoto et al.

Figure 1. ESI FTMS spectrum of [Re8ac]⁸⁺(PF₆^-)₈. The eluent was

MeCN.

ing CH₃CO₂NH₄(0.15 M).²⁹This method was useful for

isolation because of the relatively high solubilities of the

complexes in polar solvents, and the large difference in

molecular weights of the polymers in the crude products.

Chromatograms of analytical SEC for the crude products and

the isolated [Re5ac]⁵⁺

, , , and

[Re10ac]¹⁰⁺[Re15ac]¹⁵⁺

[Re20ac]²⁰⁺are shown in Figure S3 in Supporting Information.

The other Re(I) oligomers and polymers could also be isolated

from the reaction mixture by a similar method using SEC.

The isolated Re(I) oligomers and polymers were identiﬁed

by a combination of ¹H NMR, IR, electrospray ionization

Fourier transform mass spectrometry (ESI FTMS), analytical

SEC, and elemental analysis. High-resolution ESI FTMS is a

particularly powerful technique for identifying oligomers. As

an example, the mass spectrum of [Re8ac]⁸⁺(PF₆^-)₈is shown

in Figure 1. There are ﬁve peaks, each attributable to [Re8ac]⁸⁺

with a different number of PF₆^-, i.e., [M + n(PF₆^-)]^(8-n)+

(n ) 0-4); virtually no fragmentation peaks were observed.

Figure 2a shows a scale-extended spectrum of the peaks

Figure 2. ESI FTMS spectrum of the scale-extended segment for the seven

charged [M + (PF₆^-)]⁷⁺(a) and calculated isotope distribution patterns

(b).

(ii) the next units from the edge -[Re(bpy)(CO)₂]-, located

between [Re(bpy)(CO)₃]- and -[Re(bpy)(CO)₂]-; (iii) deeper

interior units -[Re(bpy)(CO)₂]- which are between two -[Re(b-

py)(CO)₂]- units. The proton signals attributed to the group (i)

were observed at lower magnetic ﬁelds than the other groups,

because of the three CO ligands which have greater π-acidity

than the phosphorus ligands, and probably because there are

only two phenyl groups on the phosphorus ligand close to the

bpy ligand, but four phenyl groups for groups (ii) and (iii).

Proton peaks attributed to the group (iii) were not observed for

[Re3ac]³⁺. The integrated areas for the protons in the group

(iii) increased for longer Re polymers: the area ratios for groups

(i), (ii), and (iii) were about 2:2:1, 2:2:2, 2:2:3, and 2:2:4 for

[Re5ac]⁵⁺to [Re8ac]⁸⁺, respectively. The relationship between

the number of Re(I) units and the ratios of the integrated areas

A(Hⁱ₅+ H₅ⁱⁱ)/A(H₆ⁱⁱⁱ) (n ) 3, 4, 6) is shown with black circles in

Figure 4 for [Re2ac]²⁺to [Re16ac]¹⁶⁺for which structures were

conclusively determined by ESI FTMS, as described above. The

good linear relationship demonstrates that this ﬁgure is useful

for determining the number of Re(I) units in those polymers

for which parent ion peaks could not be observed by ESI FTMS.

The calibration line indicates that the longest isolated polymer

made from [Re5ac]⁵⁺as a starting complex has 20.4 ( 2.0

Re(I) units (the red circle in Figure 4).

attributed to [M + PF₆]

^{- 7+}. This identiﬁcation is supported by

the strong similarities with the calculated spectrum shown in

Figure 2b, as follows: (1) the m/z values are in good agreement

with the calculated values with mass accuracy of <3.5 ppm;

(2) The separations of the individual isotope peaks are 0.1431

( 0.0001 amu, which is reliable evidence that the peaks are

due to a cation with 7+ charges; (3) the patterns for the isotope

distribution in the observed and calculated peaks are almost

identical. The other peaks observed were also in good agreement

with the calculated values. Similar results are obtained for

[Re2ac]²⁺- [Re7ac]⁷⁺. Although fragmentation peaks corre-

sponding one CO-ligand were replaced by one eluent molecule

(MeCN) were detected in the case of polymers with 10-16 Re(I)

units, the main parent ion peaks were also observed and agree

well with the calculated values. No parent peak was detected

for polymers with >16 Re(I) units.

1

Figure 3 shows aromatic proton peaks in H NMR spectra

of [Re2ac]²⁺, [Re3ac]³⁺, [Re6ac]⁶⁺, [Re8ac]⁸⁺, and [Re20-

ac]²⁰⁺measured in acetone-d₃at room temperature. Signals

attributed to the protons in the bpy ligand can be divided into

three groups: (i) edge units having structure [Re(bpy)(CO)₃]-;

FT IR spectra of the oligomers and polymers provide further

information about the number of Re(I) units. Figure 5shows IR

spectra of [Re2ac]²⁺to [Re8ac]⁸⁺in the ν(CO) region measured

in MeCN at room temperature. IR spectra reported for mono-

(29) Takeda, H.; Yamamoto, Y.; Nishiura, C.; Ishitani, O. Anal. Sci. 2006,

22, 545–549.

9

14664 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Linear-Shaped Re(I) Oligomers and Polymers with 2-20 Units

A R T I C L E S

Figure 4. Relationship between the number of Re(I) units in the oligomers

and polymers and ratios of the integrated areas of their ¹H NMR signals,

A(H₅ⁱ+ H₅ⁱⁱ)/A(Hⁱ₆ⁱⁱ) (n ) 3, 4, 6), measured in acetone-d₃at room

temperature. See the structure as shown in Figure 3 for numbering of the

protons. The red circle is the longest isolated polymer made from [Re5ac]⁵⁺

.

Figure 5. IR spectra of [Re2ac]²⁺(dotted line), [Re4ac]⁴⁺(blue line),

[Re6ac]⁶⁺(red line), and [Re8ac]⁸⁺(solid black line) measured in MeCN.

They are standardized by the absorbance at 2048 cm^-1

.

the logarithms of the molecular weights (excluding those of

counter anions) against the distribution coefﬁcient K_SEC. A

straight line can be drawn for the polymers with 6-16 Re(I)

units (eq 7), as shown in Figure 7, but the data for the shorter

oligomers could not be ﬁtted by this line. This demonstrates

that the distribution coefﬁcients (K_SEC) for longer Re(I) polymers

([Re6ac]⁶⁺to [Re16ac]¹⁶⁺) were smaller than the values

expected from the data for shorter Re(I) oligomers ([Re2ac]²⁺

to [Re5ac]⁵⁺). The shapes of the longer Re(I) polymers are

probably not rodlike in solution, but are more condensed forms,

because of aggregation. This will be discussed later.

Figure 3. Aromatic regions in ¹H NMR spectra of [Re2ac]²⁺, [Re3ac]³⁺

,

[Re6ac]⁶⁺, [Re8ac]⁸⁺, and [Re20ac]²⁰⁺measured in acetone-d₃at room

temperature.

nuclear

fac-[Re(LL)(CO)₃(PR₃)]⁺

and

cis,trans-

[Re(LL)(CO)₂(PR₃)(PR′₃)]⁺type complexes clearly indicate that

these complexes have three and two ν(CO) peaks, with similar

absorbance, respectively.^19,27,30The ratios of the areas between

the peaks at 1885 cm^-1and 2048 cm^-1, attributable to the edge

and interior units respectively, are plotted against the number

of Re(I) units in Figure 6. The number of Re(I) units in the

longest isolated polymer can also be calculated, as 20.1 ( 0.4

units for the polymers made from [Re5ac]⁵⁺based on this

ﬁgure. This result is consistent with those obtained by ¹H NMR

measurement as described above.

log M_W) -0.977K_SEC+ 5.891(for[Re6ac]⁶⁺to [Re16ac]¹⁶⁺

)

(7)

Application of eq 7 shows that the number of Re(I) units of

the longest isolated polymer made from [Re5ac]⁵⁺is 20.6 (

3.7. Although the structure of the long Re(I) polymer with >16

Re(I) units could not be determined by ESI FTMS, the logical

Analytical SEC can also be used to determine the molecular

weights of the Re(I) polymers.²⁹Figure 7 shows the plots of

1

conclusion based on the results of H NMR, IR, and SEC is

that the longest isolated polymer made from [Re5ac]⁵⁺is

(30) Smithback, J. L.; Helms, J. B.; Schutte, E.; Woessner, S. M.; Sullivan,

B. P. Inorg. Chem. 2006, 45, 2163–2174.

[Re20ac]²⁰⁺

.

9

J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008 14665

A R T I C L E S

Yamamoto et al.

Consequently, the intermolecular π-π interaction in [Re2ac]²⁺

is probably the reason why [Re2ac]²⁺has the “trans”-type

structure.

Although the other trimer [Re3et]³⁺had a similar crystal

structure to [Re3ac]³⁺, i.e. the U-shaped form shown in Figure

8c, there was no mirror plane in [Re3et]³⁺, and the torsional

angle between the Re(1)-P(1) and Re(3)-P(4) bonds in both

the edge units was 31.6° (it was 0° for that of [Re3ac]³⁺).

The main chain of the tetramer with et bridge ligands

[Re4et]⁴⁺had a circle-like structure (Figure 8d), so that the

distance between the two Re (I) ions in both the edges (6.14

Å) was shorter than the other Re-Re distances (>6.7 Å), and

the torsional angle between Re(1)-Re(2) and Re(3)-Re(4) was

very small (5.6°). This should provide a clue to the nonlinearity

in the plots of the logarithm of molecular weight versus K_SEC

of the Re(I) oligomers in the SEC analysis (Figure 7); if these

multinuclear Re(I) complexes have rod-shaped conformation in

solution, these plots should lie on a single straight line. The

X-ray crystallographic data for the trimers and the tetramer

suggest that extended structures are not feasible for the Re(I)

oligomers in the absence of intermolecular interaction, and

probably also for longer polymers. Since the K_SECvalues of

the longer polymers than the 6mer in SEC were smaller than

the values expected from the plots for the shorter oligomers

(Figure 7), the polymers must be intramolecularly aggregated,

and possibly have helical structures even in solution.

Figure 6. Relationship between the ratios of the ν(CO) peak areas due to

edge units (2048 cm^-1) and interior units (1885 cm^-1) of [Re2ac]²⁺to

[Re16ac]¹⁶⁺(black dots), and the number of Re(I) units. The red circle is

the polymer for the longest isolated polymer made from [Re5ac]⁵⁺

.

X-ray crystallographic data of some mononuclear rhenium(I)

complexes, fac-[Re(LL)(CO)₃(PR₃)]⁺and cis,trans-[Re(LL)-

(CO)₂(PR₃)₂]⁺, (LL ) bpy, 4,4′-dimethyl-bpy) have been

reported by Sullivan’s group³⁰and ours.^27a,31,32aThere is no

serious discrepancy in bond distances and angles around Re(I)

between the mono- and multinuclear complexes (Table 2).

UV-Vis Absorption Spectra. Figure 9a shows the UV-vis

absorption spectra of PF₆salts of [Re2ac]²⁺- [Re20ac]²⁰⁺in

MeCN. The lowest energy and broadband at 350 nm in the

spectrum of [Re2ac]²⁺is assigned to metal-to-ligand charge

transfer (MLCT) absorption of both Re(I) tricarbonyl

complex units, because of the similarity to those of fac-

[Re(bpy)(CO)₃(PR₃)]⁺type mononuclear complexes; the ab-

sorption at 320 nm can be assigned as an intraligand transition

of the bpy ligand (π-π*).¹⁹For the other complexes, their

MLCT absorption bands were broader and were observed at

longer wavelength, and their shapes of the MLCT absorption

differed. The complexes [Re3ac]³⁺to [Re20ac]²⁰⁺have two

types of Re(I) units, namely the two-edge tricarbonyl complex

units [Re(bpy)(CO)₃(PPh₂)-] and the interior biscarbonyl com-

plex unit(s) [-(PPh₂)Re(bpy)(CO)₂(PPh₂)-]⁺. Comparison with

the corresponding mononuclear complexes, [Re(bpy)-

(CO)₃(PPh₃)]⁺and [Re(bpy)(CO)₂(PPh₃)₂]⁺, shows that the

MLCT absorption of the biscarbonyl complex units is red-shifted

relative to that of the tricarbonyl complex units.^19,27This

difference should be due to the weaker ligand ﬁeld strength of

the phosphorus ligands than that of the CO ligand. The

difference in shape of the MLCT absorption band is therefore

understood as due to differences in the number of biscarbonyl

complex units in a polymer molecule. Figure 9b shows the

subtracted spectra UV-vis absorption spectrum of [Re2ac]²⁺

Figure 7. The logarithm of the molecular weight plotted against the

distribution coefﬁcient (K_SEC) of the Re(I) oligomers and polymers. The

red circle shows the longest isolated polymer made from [Re5ac]⁵⁺

.

Crystal Structure. X-ray crystallography was performed on

the dimer [Re2ac]²⁺(PF₆^-)₂, two trimers [Re3ac]³⁺(PF₆^-)₃and

-

[Re3et]³⁺(PF₆^-)₃, and a tetramer [Re4et]⁴⁺(PF₆

) (Figure

4

8a-d). We believe that these are the ﬁrst crystallographic data

for linear-shaped multinuclear Re(I) complexes. As shown in

Figure 8a, the dimer [Re2ac]²⁺has a center of inversion

between C(26)-C(27) of the bridge ligand ac, and the trimer

[Re3ac]³⁺has a mirror plane in the central Re(2) ion (Figure

8b). The packing diagram of [Re2ac]²⁺(PF₆^-)₂clearly shows

intermolecular π-π interaction between the bpy ligands which

coordinate two adjacent Re units to each other, as shown by

the yellow dotted lines in Figure S4 in Supporting Information.

The bpy ligand coordinated to the central Re unit of

[Re3ac]³⁺has two sets of intramolecular π-π interactions, with

two phenyl groups on the phosphorus atoms coordinating to

the central Re ion, as shown by the blue dotted lines in Figure

8b. Although the end units of [Re3ac]³⁺also show an

intramolecular π-π interaction between the bpy ligand and one

phenyl group of the phosphine ligand, there was no intermo-

lecular π-π interaction with other trimers. The torsional angle

between the P(1)-Re(1) and P(2)-Re(2) bonds of [Re2ac]²⁺

(180.0°) was also very different from [Re3ac]³⁺(81.1°).

(31) Tsubaki, H.; Tohyama, S.; Koike, K.; Saitoh, H.; Ishitani, O. Dalton

Trans. 2005, 385–395.

(32) (a) Tsubaki, H.; Sekine, A.; Ohashi, Y.; Koike, K.; Takeda, H.; Ishitani,

O. J. Am. Chem. Soc. 2005, 127, 15544–15555. (b) Tsubaki, H.;

Sugawara, A.; Takeda, H.; Gholamkhass, B.; Koike, K.; Ishitani, O.

Res. Chem. Intermed. 2007, 33, 37–48.

9

14666 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Linear-Shaped Re(I) Oligomers and Polymers with 2-20 Units

A R T I C L E S

Figure 8. ORTEP drawings of [Re2ac]²⁺(PF₆^-)₂(a), [Re3ac]³⁺(PF₆^-)₃(b), [Re3et]³⁺(PF₆^-)₃(c), and [Re4et]⁴⁺(PF₆^-)₄(d). PF₆^-and hydrogen atoms are

omitted for clarity. The ellipsoids correspond to 30% probability.

from these of [Re3ac]³⁺- [Re20ac]²⁰⁺, divided by the number

of biscarbonyl complex units. The similarity of these spectra

indicates that interaction among the complex units is not strong.

The similar subtracted spectra of [Re2et]²⁺from these for

[Re3et]³⁺to [Re7et]⁷⁺which have et as bridge ligand, are

shown in Figure 10. The spectrum of mononuclear complex

fac-[Re(bpy)(CO)₂(PPh₂Pr)₂]⁺is also shown using a red line

in Figure 10, for which the MLCT absorption band was observed

at 20 nm longer wavelength. Although the similarity of the

subtracted spectra for the oligomers shows that there is no strong

interaction among the units in [Re3et]³⁺- [Re7et]⁷⁺, it is

possible that the environment around the units in the oligomers

differs from that in the mononuclear complex, probably because

of the aggregation.

Emission. The multinuclear complexes all emit at room

temperature in a degassed MeCN solution upon excitation at

350 nm. Figure 11 shows the emission spectra of [Re2ac]²⁺to

[Re20ac]²⁰⁺, standardized by the absorbance at the excitation

wavelength 350 nm. The emission spectra of [Re2ac]²⁺had a

broad band with an emission maximum at 523 nm; the emission

showed a single exponential decay with a lifetime of 860 ns.

These are typical properties of emission from the ³MLCT

excited state of [Re(bpy)(CO)₃(PR₃)]⁺type complexes.^19,31,33

Emission from the other compounds was observed with

an emission maximum at 572 nm. The shape and energy of the

emission from all complexes except [Re2ac]²⁺were very

similar, although the quantum yields of emission were different;

a lower quantum yield was obtained from longer polymers with

more Re(I) units. It has been reported that emission from

cis,trans-[Re(bpy)(CO)₂(PR₃)₂]⁺type complexes is generally

red-shifted by 30-60 nm compared to that from fac-[Re(bpy)-

(CO)₃(PR₃)]⁺.^19,27,31,32aFigure 11 therefore indicates that ef-

ﬁcient intramolecular energy transfer occurs from the edge units

[Re(bpy)(CO)₃-] to the interior units [-Re(bpy)(CO)₂-].

The emission decay proﬁles from [Re3ac]³⁺to [Re20ac]²⁰⁺

were not single exponential. The decay curves could be ﬁtted

with double-exponential functions, with lifetimes of 11 and 833

ns in the case of [Re3ac]³⁺, but triple-exponential functions

(eq 8) were necessary to ﬁt the decay from [Re4ac]⁴⁺to

[Re20ac]²⁰⁺, where I_em(t), A_n, and τ_nrespectively denote

intensities of emission, pre-exponential factors, and lifetimes

(Table 3).

-t⁄τ₂

I_em(t) ) A₁e^-t⁄τ+ A₂e

+ A₃e^-t⁄τ³

(8)

1

Proportions of the pre-exponential factors of each component

strongly depend on both excitation and detection wavelengths.

As an example, curves a and b of Figure 12 show the decay

curve of [Re8ac]⁸⁺obtained with excitation wavelength 365

nm. As shown in Figure 12a, a monitoring wavelength of 500

nm, which is close to the emission maximum of the edge Re(I)

units, gave a main decay component with lifetime about 10 ns,

(33) Hori, H.; Johnson, F. P. A.; Koike, K.; Takeuchi, K.; Ibusuki, T.;

Ishitani, O. J. Chem. Soc., Dalton Trans. 1997, 6, 1019–1023.

9

J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008 14667

A R T I C L E S

Yamamoto et al.

-

Table 2. Selected Bond Lengths (Å) and Angles (deg) for [Re2ac]²⁺(PF₆^-)₂, [Re3ac]³⁺(PF₆^-)₃, [Re3et]³⁺(PF₆^-)₃, and [Re4et]⁴⁺(PF₆

)

4

[Re2ac]²⁺(PF₆^-

)

2

[Re4et]⁴⁺(PF₆^-

)

4

edge unit

interior unit

Bond Lengths

Re-P

Re-N

Re-C

2.499(11)

2.472(4), 2.490(4)

2.404(3), 2.408(4)

2.405(3), 2.418(3)

2.174(10), 2.202(10)

2.106(10), 2.178(9)

1.777(19), 1.933(14)

1.917(13), 1.927(13)

2.177(5)

2.159(5)

1.966(5)^a

1.933(7)^b

1.934(7)^b

1.087(7)^a

1.124(9)^b

1.128(8)^b

7.676(2)

4.746(3)

2.133(10), 2.161(9)

2.149(12), 2.177(12)

2.023(15)^a, 1.942(15)^b

1.906(16)^b, 1.945(15)^a

1.908(12)^b, 1.898(14)^b

1.127(16)^a, 1.146(16)^b

1.149(16)^b, 1.149(16)^a

1.161(14)^b, 1.146(14)^b

6.1204(5)

C-O

1.119(14), 1.249(19)

1.147(14), 1.141(14)

Re-Re

P-P

7.1551(6)^d

4.521(3), 4.499(3), 4.479(5)

Bond Angles

87.7(3), 85.2(3)

P-Re-N

P-Re-C^b

81.72(12)

90.84(13)

87.67(18)

96.60(19)

74.6(2)

91.0(3)

175.66(18)

-

90.0(3), 90.4(3)

86.3(3), 90.0(3)

89.2(4), 94.8(4)

88.3(4), 95.1(4)

74.7(4), 75.4(5)

89.4(5), 87.0(6)

178.1(4), 176.0(4)

-

90.2(3), 89.2(2)

88.8(4), 92.8(3)

86.5(4), 92.5(4)

74.7(3), 73.9(4)

91.0(5), 94.6(6)

-

N-Re-N

C^b-Re-C^b

P-Re-C^a

P-ReP

176.3(10), 179.5(11)

Re^e-Re^f-Re^f

-

83.59(1), 87.28(1)

[Re3ac]³⁺(PF₆^-

)

3

[Re3et]³⁺(PF₆^-

)

3

edge unit

interior unit

edge unit

interior unit

Bond Lengths

Re-P

2.4507(9)

2.166(3)

2.171(3)

2.3895(9)

2.4927(12), 2.4724(11)

2.161(4), 2.170(4)

2.186(4), 2.166(4)

1.949(5)^a, 1.912(5)^b

1.922(5)^b, 1.974(5)^a

1.915(6)^b, 1.909(6)^b

1.146(6)^a, 1.150(6)^b

1.149(6)^b, 1.117(5)^a

1.151(6)^b, 1.153(6)^b

8.1244(3)^c

2.4119(13), 2.4378(13)

2.174(4), 2.179(3)

Re-N

2.170(4), 2.185(4)

1.910(5), 1.921(4)

Re-C

1.950(4)^a

1.922(4)^b

1.939(5)^b

1.139(5)^a

1.145(4)^b

1.159(5)^b

10.0293(3)^c

1.904(5), 1.911(5)

1.163(5), 1.147(5)

-

C-O

1.155(6), 1.152(6)

Re-Re

P-P

-

4.7172(12)

4.5490(16), 4.5449(14)

Bond Angles

P-Re-N

P-Re-C^b

87.32(8)

91.91(7)

86.12(11)

91.31(13)

74.65(11)

91.17(17)

176.64(12)

-

87.82(2), 92.01(2)

88.56(10), 87.05(10)

85.91(11), 91.00(11)

86.72(15), 96.37(16)

87.47(10), 88.26(10)

90.57(15), 90.91(14)

91.00(15), 92.94(16)

74.23(16), 75.31(15)

91.2(2), 90.5(2)

179.16(16), 178.22(17)

-

87.67(2), 92.56(2)

N-Re-N

C^b-Re-C^b

P-Re-C^a

P-Re-P

74.50(15)

89.95(19)

-

74.78(13)

92.7(2)

-

173.07(4)

176.45(4)

Re^e-Re^f-Re^f

85.93(1)

69.15(1)

^aThe axial CO ligand, which is trans relative to the phosphorus ligand. ^bThe equatorial CO ligand, which is cis relative to the phosphorus ligand.

^cDistance between the edge units. ^dDistance between interior units. ^eThe edge unit. ^fThe interior unit.

and minors with 100 and 734 ns. The ﬁrst component with a

lifetime 10 ns, on the other hand, was observed as a rise by

changing the detection wavelength to 650 nm, where emission

from the interior Re(I) units is mainly observed (inlet in Figure

12b). The other two components were still observed as decays

with τ ) 113 and 750 ns, respectively (Figure 12b). Only two

decay components, with lifetimes 100 and 710 ns, were observed

using an excitation wavelength of 400 nm, which is largely

absorbed by the interior Re(I) units, and a detection wavelength

of 600 nm (Figure S5 in Supporting Information). Similar triple-

exponential functions were also necessary to ﬁt the decay data

for the et complexes [Re4et]⁴⁺- [Re7et]⁷⁺, with lifetimes of

3-6 ns, ∼120 ns, and ∼500 ns (Table 4). These results clearly

indicate that the shortest component is due to emission from

the shape of the emission spectra from each of the three observed

species has been extracted from the time-resolved emission

spectra of [Re8ac]^{8+ 34}

The fact that the 10 ns component has

.

an emission maximum around 520 nm, which is similar to that

from [Re2ac]²⁺, supports the identiﬁcation. If the rate constants

of both radiative and nonradiative decay from the ³MLCT

excited-state of the edge Re(I) units in [Re8ac]⁸⁺are same as

those from [Re2ac]²⁺, them the rate constant of energy transfer

from the excited edge Re(I) unit to the interior Re(I) unit (k_et)

can be calculated as k_et) k - k′, where k is the observed rate

3

constant of decay from the MLCT excited-state of the edge

Re(I) units in [Re8ac]⁸⁺and k′ is the sum of the radiation and

nonradiative decay constants of [Re2ac]²⁺. Table 3 summarizes

the energy transfer rates for [Re3ac]³⁺-[Re20ac]²⁰⁺with their

photophysical properties; faster rate constants were observed

3

the MLCT excited-state of the edge Re(I) units. In Figure 13

9

14668 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Linear-Shaped Re(I) Oligomers and Polymers with 2-20 Units

A R T I C L E S

Figure 9. UV-vis absorption spectra of MeCN solutions containing [Re2ac]²⁺to [Re20ac]²⁰⁺(a). Subtracted spectra UV-vis absorption spectrum of

[Re2ac]²⁺from those of [Re3ac]³⁺to [Re20ac]²⁰⁺, divided by the number of biscarbonyl complex units (b).

aggregated in an MeCN solution. X-ray crystallographic data

for [Re4et]⁴⁺shows that two edge Re(I) units had a shorter

distance even than the distance from the next-door interior unit

(Figure 8d). Aggregation in a longer Re(I) polymer therefore

probably gives more frequent opportunity for collisions between

the excited edge unit and the interior units during the conforma-

tion changes in the solution.

The other two components of the emission decay with

lifetimes about 100 and 750 ns should be attributed to emission

from the interior Re(I) units. This is because, as shown in Figure

13, their emission maxima were respectively 575 and 595 nm

and are similar to those from the ³MLCT excited-state of

cis,trans-[Re(bpy)(CO)₂(PR₃)₂]⁺type mononuclear complexes.

We have recently reported^32athat intramolecular π-π and/or

CH-π interaction occurs between the diimine ligand and the

aryl groups on the phosphorus ligand in [Re(LL)(CO)₂(PAr₃)₂]⁺

(LL ) diimine ligand such as 4,4′-dimethyl-2,2′-bpy); such

interligand interaction causes a blue-shift in the emission and

longer lifetime of the ³MLCT excited state, which can be

explained as follows. The interaction between the ligands gives

rise to a smaller polarization in the ³MLCT excited state, because

the electron located mainly on the diimine ligand is partially

dispersed to the aryl groups. It should reduce the shift between

Figure 10. Subtracted spectra UV-vis absorption spectrum of [Re2et]²⁺

from those of [Re3et]³⁺- [Re7et]⁷⁺, divided by the number of the

biscarbonyl complex units; the red line is the UV-vis absorption spectrum

of fac-[Re(bpy)(CO)₂(PPh₂Pr)₂]⁺in MeCN.

3

the energy surface minima of the MLCT and ground states

3

along the coordination axis. Emission from the MLCT to the

ground state should then be observed at higher energy, and the

Franck-Condon factor becomes smaller, making nonradiative

decay slower. We conclude that there are at least two main

conformations of [Re4ac]⁴⁺-[Re20ac]²⁰⁺, respectively; one has

interaction between the bpy ligand and the phenyl groups on

the ac ligand (λ_em^max) 575 nm, τ = 750 ns), but the other has

max

no interaction or much weaker interaction between them (λ_em

) 595 nm, τ = 100 ns). Similar phenomena were observed in

for [Re4et]⁴⁺- [Re7et]⁷⁺(τ = 120 ns, ∼500 ns: Table 4), and

the same explanation applies. This is also supported by the

fact that emission of the mononuclear complex cis,trans-

[Re(bpy)(CO)₂(PPh₂Pr)₂]⁺as a model of the interior units in

Figure 11. Emission spectra from degassed MeCN solutions containing

[Re2ac]²⁺to [Re20ac]²⁰⁺standardized by the absorbance at the excitation

wavelength 350 nm.

(34) This was done by normalizing the time resoled emission spectra

containing emission from all species. The emission spectrum of the

750 ns component was taken as the time resolved spectrum detected

after 1 µs where emission of other species had already decayed. The

emission from the 100 ns component was achieved by subtracting the

normalized spectrum after 1 µs from the spectrum at 40 ns. Finally

the emission spectrum of the 10 ns component was approximated by

subtracting the spectrum at 40 ns from the spectrum after 10 ns.

for a longer Re(I) polymer. Similar phenomena were observed

in complexes with et as bridge ligands, i.e. [Re2et]²⁺-[Re7et]⁷⁺

(Table 4). As described in the Isolation and Identiﬁcation

section, the SEC analysis data strongly indicates that the

“longer” Re(I) polymers with more than 6 Re(I) units, are

9

J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008 14669

A R T I C L E S

Yamamoto et al.

Table 3. Photophysical Properties of [Re2ac]²⁺to [Re20ac]²⁰⁺in a Deoxygenated Acetonitrile Solution at 25 °C, and Energy Transfer

Rates from the Edge Unit to the Interior Unit in [Re3ac]³⁺to [Re20ac]²⁰⁺

τ_em^d/ns

observed at 480 nm

observed at 575 nm

c

complex^a

λ_em^b/nm

Φ_em

τ₁

τ₂

τ₃

τ₁

τ₂

τ₃

k_et/10⁷s^-1

[Re2ac]²⁺

[Re3ac]³⁺

[Re4ac]⁴⁺

[Re5ac]⁵⁺

[Re6ac]⁶⁺

[Re8ac]⁸⁺

[Re10ac]¹⁰⁺

[Re12ac]¹²⁺

[Re15ac]¹⁵⁺

[Re16ac]¹⁶⁺

[Re20ac]²⁰⁺

523

572

571

572

0.072

0.073

0.066

0.062

0.058

0.056

0.053

0.051

0.049

0.048

0.046

865 (100)

11 (91)

11 (73)

11 (83)

11 (57)

10 (86)

8 (81)

-

865 (100)

-

833 (9)

798 (20)

796 (16)

768 (38)

763 (12)

720 (8)

758 (14)

-

833 (100)

798 (88)

796 (95)

768 (88)

763 (89)

720 (79)

758 (85)

764 (80)

757 (78)

747 (86)

8.98

128 (7)

112 (1)

129 (5)

110 (2)

168 (12)

118 (4)

162 (4)

64 (3)

132 (8)

128 (12)

112 (5)

129 (12)

110 (11)

168 (21)

118 (15)

162 (20)

64 (22)

132 (14)

8.98

9.88

12.38

14.17

24.88

19.88

24.88

7 (82)

4 (96)

5 (87)

4 (92)

757 (10)

-

^aAll complexes were PF₆salts. The excitation wavelength was 350 nm. ^bEmission maximum. ^cQuantum yield of emission. ^dLifetime. Numbers in

parentheses are percentages of pre-exponential factors, i.e., A_n/∑³_m)1A_m(see eq 8).

Figure 12. Emission decay curves of [Re8ac]⁸⁺obtained at excitation wavelength of 365 nm. Monitor wavelength: 500 nm (a) and 650 nm (b).

Table 4. Photophysical Properties of [Re2et]²⁺to [Re7et]⁷⁺in a Deoxygenated Acetonitrile Solution at 25 °C, and Energy Transfer Rates

from the Edge Unit to the Interior Unit in [Re3et]³⁺- [Re7et]⁷⁺

τ_em^d/ns

observed at 500 nm

observed at 600 nm

c

complex^a

λ_em^b/nm

Φ_em

τ₁

τ₂

τ₃

τ₁

τ₂

τ₃

k_et10⁷s^-1

[Re2et]²⁺

[Re3et]³⁺

[Re4et]⁴⁺

[Re5et]⁵⁺

[Re7et]⁷⁺

543

626

628

0.135

0.011

0.009

0.008

0.007

865 (100)

6 (83)

4 (99.7)

4 (100)

3 (100)

-

865 (100)

-

556 (8)

515 (5)

484 (6)

-

143 (17)

129 (0.3)

-

143 (100)

129 (92)

117 (95)

123 (94)

1.66

2.49

3.32

-

^aAll complexes were PF₆salts. The excitation wavelength was 350 nm. ^bEmission maximum. ^cQuantum yield of emission. ^dLifetime. Numbers in

parentheses are percentages of pre-exponential factors, i.e., A_n/∑³_m)1A_m(see eq 8).

[Re3et]³⁺- [Re7et]⁷⁺, exhibits a double exponential decay

with lifetimes of 130 and 500 ns. It is noteworthy that some

interactions between the bpy ligand and the phenyl groups on

[Re3ac]³⁺, [Re3et]³⁺, and [Re4et]⁴⁺were observed in crystals

(Figure 8).

the ac complexes, the component with longer lifetime was

dominant (∼90%), but the shorter lifetime component was

dominant (>90%) for the et complexes. This suggests that not

only the phenyl groups but also the CtC group on the ac ligand

can generate π-π interaction with the bpy ligand.

A clear difference in emission behavior between the two series

of multinuclear Re(I) complexes with et and ac as bridge ligands

is the ratio of the pre-exponential factor obtained for the

components with lifetimes 100-130 ns and 500-800 ns. For

The quantum yield of emission decreased in the longer Re(I)

polymers in both series, as shown in Figure 11 and Tables 3

and 4. However, there were no signiﬁcant differences in the

emission lifetimes from the interior units, except for the trimer,

9

14670 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Linear-Shaped Re(I) Oligomers and Polymers with 2-20 Units

A R T I C L E S

be caused by the intramolecular aggregation of the polymer

molecules in an MeCN solution.

Conclusion

We applied photochemical ligand substitution reactions of

Re(I) diimine complexes with a phosphorus ligand, to ﬁnd

systematic synthetic routes for linear-shaped rhenium(I) oligo-

mers and polymers bridged with bidentate phosphorus ligands.

Oligomers and polymers with up to 20 Re(I) units were isolated

using SEC and were accurately identiﬁed by a combination of

¹H NMR, IR, ESI FTMS, analytical SEC, and elemental

analysis. All of the synthesized oligomers and polymers were

emissive at room temperature in solution. For oligomers and

polymers with g3 Re(I) units, energy transfer from the edge

unit to the interior unit occurs with a rate constant of (0.9 ×

10⁸)-(2.5 × 10⁸) s^-1. Crystal structures were obtained of some

trimers and a tetramer, showing interligand π-π interaction

between the diimine ligand and the phenyl groups on the

phosphorus ligand. Both emission and analytical SEC data

indicate that the Re(I) polymers aggregate intramolecularly in

an MeCN solution. Each unit in the Re(I) oligomers and

polymers potentially has photocatalytic activities for CO₂

reduction, and this is currently under investigation in our

laboratory.

Figure 13. Time resolved emission spectra of [Re8ac]⁸⁺. Black, red, and

blue lines are emission spectra with lifetime of 10, 100, and 750 ns,

respectively.³⁴

Experimental Section

Instrumentation and Measurements. IR spectra were recorded

in an MeCN solution with a JASCO FT/IR-610 spectrometer at

1-cm^-1resolution. ¹H and H,H COSY NMR spectra and ³¹P NMR

spectra were measured in an acetone-d₆solution using a JEOL JNM-

AL400 (400 MHz). Residual protons of acetone-d₆and the

phosphorus atom of H₃PO₄were used as internal and external

standards for measurements. Electrospray ionization mass spec-

troscopy (ESI MS) took place using a Shimadzu LCMS-2010A

mass spectrometer or a Thermo Fisher Scientiﬁc LTQ Orbitrap ESI

FTMS spectrometer. UV-vis absorption spectra were recorded in

an MeCN solution with a JASCO V-565 spectrophotometer.

Emission spectra were recorded at 25 °C using a JASCO FP-6500

spectrophotometer, with correction for the detector sensitivity

determined using correction data supplied by JASCO. The sample

solutions were degassed by the freeze-pump-thaw method before

the emission measurements. Emission quantum yields were evalu-

Figure 14. Dependence of Φ_emon toluene content in an MeCN/toluene

mixed solution.

and the ratios of the pre-exponential factors in any of the

polymers. The quantum yields and the lifetimes can be deduced

from eqs 9 and 10. The nonradiative decay constant (k_nr) should

be much larger than the radiative decay constant (k_r), because

the quantum yield of emission is less than 10% except for that

of [Re3et]³⁺(11%). Consequently, the change of Φ_emdepending

on the number of Re(I) units in the Re(I) polymer should be

reﬂected in differences of k_r, whereas k_nrshould not change.

2+

ated with Ru(bpy)₃(Φ_em) 0.062) in degassed acetonitrile as a

standard.

Separation and Analysis Using Size Exclusion Chroma-

tography. Separation of the Re oligomer and polymer complexes

was achieved by size exclusion chromatography (SEC) using a pair

of Shodex PROTEIN KW-2002.5 columns (300 mm × 20.0 mm

i.d.) with a KW-LG guard-column (50 mm × 8.0 mm i.d.) and a

JAI LC-9201 recycling preparative HPLC apparatus with a JASCO

870-UV detector. The eluent was a 1:1 (v/v) mixture of methanol

and acetonitrile with 0.15 M CH₃CO₂NH₄, and the ﬂow rate was

5.0 mL min^-1. For analysis by SEC, we used a pair of Shodex

PROTEIN KW-802.5 (300 mm × 8.0 mm i.d.) with a KW-LG

guard-column (50 mm × 6.0 mm i.d.), a JASCO 880-51 degasser,

a 880-PU pump, a MD-2010 Plus UV-vis photodiode-array

detector and a Rheodyne 7125 injector. The detection wavelength

was chosen as 360 nm because all of the complexes analyzed have

a strong MLCT and/or π-π* absorption bands around 350-500

nm. The column temperature was kept at 40 ( 0.1 °C using a

JASCO 860-CO column-oven. The eluent was a 1:1 (v/v) mixture

of methanol and acetonitrile with 0.3 M CH₃CO₂NH₄, and the ﬂow

rate was 0.5 mL min^-1. Details have been reported elsewhere.²⁹

k_r

Φ_em

)

(9)

k_r+ k_nr

1

τ )

(10)

k_r+ k_nr

Figure 14 shows the dependence of Φ_em, for [Re3ac]³⁺

,

[Re5ac]⁵⁺, [Re8ac]⁸⁺, and [Re12ac]¹²⁺, on the toluene content

in MeCN/toluene mixed solutions. In solution containing more

toluene, Φ_emis greater for the Re(I) polymers. The increase is

more pronounced for longer Re(I) polymers. On the other

hand, the Φ_emvalue of the mononuclear complex cis,trans-

[Re(bpy)(CO)₂(PPh₃)₂]⁺decreased in solutions containing even

more toluene, as shown in Figure 14. Addition of toluene to an

MeCN solution probably weakened the hydrophobic (i.e., π-π

and CH-π) interaction in the Re(I) polymers, and the aggrega-

tion of the Re(I) polymers should be partially resolved.³⁵In

other words, the decrease of k_rfor longer Re(I) polymers might

(35) Addition of methanol (50%) instead of toluene did not cause any

change in the emission behavior of the complexes.

9

J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008 14671

A R T I C L E S

Yamamoto et al.

Photochemical Reactions. For the photochemical ligand sub-

stitution reaction, the solution was irradiated by an Eikosha EHB-

WI-500 high-pressure mercury lamp (500 W) with a uranium glass

ﬁlter (>330 nm) in a Pyrex doughnut-form cell with bubbling of a

N₂or Ar gas. During irradiation, both the reaction vessel and the

light source were cooled with tap water.

light, giving fac-[Re(CO)₃(bpy)(η¹-ac)](CF₃SO₃), quantitatively.

The solution was irradiated using a high-pressure mercury lamp

with a uranium glass ﬁlter for 12 h, and the solvent was then

evaporated under reduced pressure. The residual red solid was

washed several times with degassed ether. Yield: 82%. ESI MS in

MeCN (m/z): 1187, [M]⁺. IR (MeCN): ν_CO/cm^-1) 1956, 1886.

-

[Re(bpy)(CO)₃(ac)Re(bpy)(CO)₃](CF₃SO₃)₂, [Re2ac]²⁺(CF₃SO₃^-)₂.

A THF solution (100 mL) of fac-Re(CO)₃(bpy)(CF₃SO₃) (700 mg,

1.22 mmol) and 0.5 equiv of ac (240 mg, 0.61 mmol) was reﬂuxed

for 3 days in dim light. The precipitated light-yellow powder was

ﬁltered off, washed with diethylether, and dried in a vacuum. Yield:

95%. Anal. Calcd for C₅₄H₃₆F₆N₄O₁₂P₂Re₂S₂: C, 41.97; H, 2.35; N,

Crystal Structure Determination. The single crystals of PF₆

salts of [Re2ac]²⁺, [Re3ac]³⁺, [Re3et]³⁺, and [Re4et]⁴⁺were

obtained by slow diffusion of diethyl ether into an MeCN or an

acetone solution containing the complex. Data of [Re2ac]²⁺were

collected at 25 °C on an AFC7R, and data of [Re3ac]³⁺, [Re3et]³⁺

,

and [Re4et]⁴⁺were collected at -50 and -150 °C on a Rigaku

Mercury CCD with graphite monochromated Mo KR radiation

(λ ) 0.7107 Å). The crystal data of these were yellow prisms of

approximate dimensions of 0.20 mm × 0.20 mm × 0.20 mm

([Re2ac]²⁺), 0.30 mm × 0.10 mm × 0.10 mm ([Re3ac]³⁺), 0.15

mm × 0.10 mm × 0.06 mm ([Re3et]³⁺), and 0.14 mm × 0.08

mm × 0.03 mm ([Re4et]⁴⁺). For all the crystals, the structures

were solved by SHELX-97 programs.³⁶Non-hydrogen atoms were

reﬁned anisotropically, and hydrogen atoms were generated

geometrically.

1

3.63. Found: C, 42.21; H, 2.63; N, 3.85. H NMR (δ, 400 MHz,

CD₃COCD₃): 8.78 (d, 4H, J ) 5.6 Hz, bpy-6,6′), 8.28 (d, 4H, J ) 8.5

Hz, bpy-3,3′), 8.12 (dd, 4H, J ) 8.5, 7.7 Hz, bpy-4,4′), 7.65 (m, 4H,

Ph-p), 7.54-7.44 (m, 8H, Ph-m), 7.46 (dd, 4H, J ) 7.7, 5.6 Hz, bpy-

5,5′), 7.25 (m, 8H, Ph-o). ³¹P NMR (δ, 400 MHz, CD₃COCD₃): 3.30

(s). IR (MeCN): ν_CO/cm^-1) 2049 (s), 1965 (m), 1931 (m). ESI MS

in MeCN (m/z): 623 [M]²⁺

.

[Re(bpy)(CO)₃(ac)Re(bpy)(CO)₂(CF₃SO₃)](CF₃SO₃), [Re2ac-

(CF₃SO₃)₁]⁺(CF₃SO₃^-). A solution of CF₃SO₃^-salts of [Re2ac]²⁺

(150 mg, 0.10 mmol) in 200 mL of THF was irradiated for 25

min. About half of the THF was removed by evaporation, and then

diethylether was added to the concentrated solution. Precipitated

red powder was ﬁltered off, washed with diethylether, and then

dried in a vacuum. Yield: 97%. ESI MS in MeCN (m/z): 630 [M

Emission Lifetime Measurement. An acetonitrile solution of

the metal complex was degassed by means of the freeze-pump-thaw

method and transferred into a 10 mm × 10 mm × 40 mm quartz

cuvette. Emission lifetimes were measured using a Horiba NAES-

1100 time-correlated single-photon-counting system. The sample

solutions were excited by a NFL-111 ns H₂lamp with a proper

band-pass ﬁlter (Toshiba U350). Decay proﬁle simulations were

performed by a nonlinear least-squares method.

- CF₃SO₃+ MeCN]²⁺

.

[Re(bpy)(CO)₃(ac)Re(bpy)(CO)₂(η¹-ac)](CF₃SO₃)₂, [Re2ac(η¹-

ac)₁]²⁺(CF₃SO₃^-)₂. A dicholoromethane solution (100 mL) of

[Re2ac(CF₃SO₃)₁]⁺(CF₃SO₃^-) (60 mg, 0.04 mmol) and ac (50 mg,

0.13 mmol) was heated at 40 °C for 1 day in dim light. About half

of CH₂Cl₂was removed by evaporation, and diethylether was then

added to the concentrated solution. The precipitated orange powder

was ﬁltered off, washed with diethylether, and dried in a vacuum.

Measurement of Time-Resolved Emission Spectra. Emission

lifetime measurements were made using the second harmonic of

Ti:sapphire laser (SpectraPhysics, Tsunami) as an excitation light

source. The repetition rate was reduced to 0.1 MHz by an EO

modulator (Conoptics). The emission was detected at magic angle

conﬁguration using a polarizer and a half-wave-plate. A photo-

multiplier (Hamamatsu Photonics, R3809U-50) with an ampliﬁer

(Hamamatsu Photonics, C5594) and a counting board (PicoQuanta,

PicoHarp 300) were used to detect the signal. A monochromator

(Oriel, 77250) was placed in front of the photomultiplier to select

monitoring wavelength. The system response time was found to

be 32 ps fwhm from light scattered from a colloidal solution. The

excitation intensity effect on the emission decay was measured using

the third harmonic of DCR-3 (Qaunta Ray, fwhm 5 ns). Emission

was detected by a photomultiplier (Hamamatsu Photonics, R1563U-

01) placed after the monochromator (Oriel 77250). The output of

the photomultiplier was connected to a fast oscilloscope (LeCroy,

1.5 GHz 9662C) and sent to PC for further analysis. The response

time of the detection system was approximately 700 ps. For the

measurement of time-resolved emission spectra, we used a gated-

diode array detector with a polychromator (Hamamatsu Photonics,

PMA-50, gate time of 5 ns).

Materials. THF was distilled from Na/benzophenone just before

use. Acetonitrile was dried three times over P₂O₅and then distilled

from CaH₂prior to use. Dichloromethane was dried over CaH₂prior

to use. All puriﬁed solvents were kept under N₂before use. Spectral-

grade solvents were used for the spectroscopic measurements. Other

reagents and solvents were purchased reagent-grade from Kanto

Chemical Co., Tokyo Kasei Co., Wako Pure Chemical Industries,

and Aldrich Chemical Co. and were used without further puriﬁcation.

Synthesis. The standard Schlenk techniques were employed for

synthesis. fac-Re(CO)₃(bpy)(CF₃SO₃) was prepared according to

the method in the literature.^22b

Yield: 90%. ESI MS in MeCN (m/z): 807 [M]²⁺

.

[{Re(bpy)(CO)₃(ac)}₂Re(bpy)(CO)₂](PF₆)₃, [Re3ac]³⁺(PF₆^-)₃. A

solution of [Re2ac(η¹-ac)₁]²⁺(CF₃SO₃^-)₂(65 mg, 0.03 mmol) and

fac-Re(CO)₃(bpy)(CF₃SO₃) (23 mg, 0.04 mmol) in 100 mL of THF/

acetone (1:1) was stirred at room temperature for 1 day, then at 40

°C for 1 day in dim light. The solution was then evaporated. The

residue was separated using SEC. The band that included the

product was collected and evaporated under reduced pressure. A

methanol solution of residue was added dropwise to a concentrated

MeOH solution of NH₄PF₆. The precipitated yellow powder was

ﬁltered off, washed with diethylether, and dried in a vacuum. Yield:

79%. Anal. Calcd for C₉₀H₆₄F₁₈N₆O₈P₇Re₃: C, 43.68; H, 2.61; N,

1

3.40. Found: C, 43.80; H, 2.56; N, 3.29. H NMR (δ, 400 MHz,

CD₃COCD₃): 8.71 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of Re(bpy)-

(CO)₃-), 8.22 (d, 4H, J ) 8.0 Hz, bpy-3,3′ of Re(bpy)(CO)₃-), 8.07

(dd, 4H, J ) 8.0, 7.6 Hz, bpy-4,4′ of Re(bpy)(CO)₃-), 7.97 (d, 2H,

J ) 5.2 Hz, bpy-6,6′ of Re(bpy)(CO)₂-), 7.78 (d, 2H, J ) 8.0 Hz,

bpy-3,3′ of Re(bpy)(CO)₂-), 7.61-7.59 (m, 8H, Ph-p), 7.57 (dd,

2H, J ) 8.0, 7.2 Hz, bpy-4,4′ of Re(bpy)(CO)₂-), 7.54-7.44 (m,

16H, Ph-m, and Ph-o), 7.42 (dd, 4H, J ) 7.6, 5.2 Hz, bpy-5,5′ of

Re(bpy)(CO)₃-), 7.30-7.10 (m, 16H, Ph-m, Ph-p, and Ph-o), 6.80

(dd, 2H, J) 7.2, 5.2 Hz, bpy-5,5′ of Re(bpy)(CO)₂-). ³¹P NMR (δ,

400 MHz, CD₃COCD₃): 7.87 (s), 2.64 (s). IR (MeCN): ν_CO/cm^-1

) 2048 (s), 1964 (s), 1956 (m), 1930 (m), 1887 (m). ESI MS in

MeCN (m/z): 680 [M]³⁺, 1092 [M + PF₆]²⁺

.

[Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}₂Re(bpy)(CO)₃](PF₆)₄,

[Re4ac]⁴⁺(PF₆^-)₄. A dichloromethane solution (100 mL) of

[Re2ac(CF₃SO₃)₁]⁺(CF₃SO₃^-) (200 mg, 0.13 mmol) and a 0.5

equiv of ac (26.0 mg, 0.066 mmol) was stirred at room temperature

for 1 day, and then at 40 °C for 1 day in dim light. The solution

was then evaporated. The residue was separated using SEC. The

band including the product was collected and evaporated under

reduced pressure. A methanol solution of the residue was added

dropwise to a concentrated MeOH solution of NH₄PF₆. The

precipitated yellow powder was ﬁltered off, washed with diethyl-

cis,trans-[Re(bpy)(CO)₂(η¹-ac)₂](CF₃SO₃). A tetrahydrofuran

solution (100 mL) of fac-Re(CO)₃(bpy)(CF₃SO₃) (100 mg, 0.17

mmol) with 5 equiv of bis(diphenylphosphino)acetylene (ac) (350

mg, 0.87 mmol) were stirred for 1 day at room temperature in dim

(36) Sheldrick, G. M. SHELX-97. Programs for Crystal Structure Analysis;

University of Go¨ttingen: Germany, 1997.

9

14672 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Linear-Shaped Re(I) Oligomers and Polymers with 2-20 Units

A R T I C L E S

ether, and then dried in a vacuum. Yield: 72%. Anal. Calcd for

Hz, bpy-6,6′ of (iii)Re(bpy)(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-

3,3′ of (ii)Re(bpy)(CO)₂-), 7.63 (d, 4H, J ) 8.4 Hz, bpy-3,3′

of (iii)Re(bpy)(CO)₂-), 7.56 (dd, 4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of

(ii)Re(bpy)(CO)₂-), 7.50 (dd, 4H, J ) 8.4, 6.4 Hz, bpy-4,4′ of

(iii)Re(bpy)(CO)₂-), 7.61-7.55 (m, 16H, Ph-p), 7.45-7.38 (m, 34H,

Ph-m, and Ph-o), 7.36 (dd, 4H, J ) 7.6, 5.2 Hz, bpy-5,5′ of

Re(bpy)(CO)₃-), 7.30-7.10 (m, 50H, Ph-p, and Ph-o), 6.77 (dd,

4H, J ) 8.0, 5.2 Hz, bpy-5,5′ in (ii)Re(bpy)(CO)₂-), 6.73 (dd, 4H,

J ) 5.2, 6.4 Hz, bpy-5,5′ of (iii)Re(bpy)(CO)₂-). ³¹P NMR (δ, 400

C₁₂₈H₉₂F₂₄N₈O₁₀P₁₀Re₄: C, 45.05; H, 2.72; N, 3.28. Found: C, 44.78;

H, 2.79; N, 3.15.¹H NMR (δ, 400 MHz, CD₃COCD₃): 8.70 (d,

4H, J ) 5.1 Hz, bpy-6,6′ of Re(bpy)(CO)₃-), 8.21 (d, 4H, J ) 8.6

Hz, bpy-3,3′ of Re(bpy)(CO)₃-), 8.05 (dd, 4H, J ) 8.6, 7.6 Hz,

bpy-4,4′ of Re(bpy)(CO)₃-), 7.88 (d, 4H, J ) 5.4 Hz, bpy-6,6′ of

Re(bpy)(CO)₂-), 7.70 (d, 4H, J ) 8.5 Hz, bpy-3,3′ in Re(bpy)-

(CO)₂-), 7.59-7.53 (m, 16H, Ph-p), 7.51 (dd, 4H, J ) 8.5, 8.0 Hz,

bpy-4,4′ of Re(bpy)(CO)₂-), 7.45-7.38 (m, 28H, Ph-m, and Ph-o),

7.36 (dd, 4H, J ) 7.6, 5.1 Hz, bpy-5,5′ of Re(bpy)(CO)₃-),

7.30-7.10 (m, 16H, Ph-p, and Ph-o), 6.77 (dd, 4H, J ) 8.0, 5.4

Hz, bpy-5,5′ in Re(bpy)(CO)₂-). ³¹P NMR (δ, 400 MHz,

CD₃COCD₃): 7.51 (s), 2.64 (s). IR (MeCN): ν_CO/cm^-1) 2048 (s),

1962 (s), 1955 (m), 1930 (m), 1884 (m). ESI MS in MeCN (m/z):

MHz, CD₃COCD₃): 7.51 (s), 7.14 (s), 2.56 (s). IR (MeCN): ν_CO

cm^-1) 2048 (s), 1963 (b), 1957 (s), 1930 (m), 1886 (s). ESI MS

in MeCN (m/z): 736 [M]⁶⁺, 913 [M + PF₆]⁵⁺

/

.

[Re8ac]⁸⁺(PF₆^-)₈: Yield 3% based on [Re4ac]⁴⁺(PF₆^-)₄used.

Calcd for C₂₈₀H₂₀₄F₄₈N₁₆O₁₈P₂₂Re₈: C, 46.94; H, 2.87; N, 3.13.

Found: C, 47.17; H, 3.14; N, 3.33. ¹H NMR (δ, 400 MHz,

CD₃COCD₃): 8.71 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of Re(bpy)-

(CO)₃-), 8.22 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of Re(bpy)(CO)₃-), 8.07

(dd, 4H, J ) 8.4, 7.6 Hz, bpy-4,4′ of Re(bpy)(CO)₃-), 7.89 (d, 4H,

J ) 5.2 Hz, bpy-6,6′ of (ii)Re(bpy)(CO)₂-), 7.82 (d, 8H, J ) 5.2

Hz, bpy-6,6′ of (iii)Re(bpy)(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-

3,3′ of (ii)Re(bpy)(CO)₂-), 7.63 (d, 8H, J ) 8.4 Hz, bpy-3,3′

of (iii)Re(bpy)(CO)₂-), 7.56 (dd, 4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of

(ii)Re(bpy)(CO)₂-), 7.50 (dd, 8H, J ) 8.4, 6.4 Hz, bpy-4,4′ of

(iii)Re(bpy)(CO)₂-), 7.61-7.55 (m, 16H, Ph-p), 7.45-7.38 (m, 70H,

Ph-m, and Ph-o), 7.36 (dd, 4H, J ) 7.6, 5.2 Hz, bpy-5,5′ of

Re(bpy)(CO)₃-), 7.30-7.10 (m, 54H, Ph-p, and Ph-o), 6.77 (dd,

4H, J ) 8.0, 5.2 Hz, bpy-5,5′ in (ii)Re(bpy)(CO)₂-), 6.73 (dd, 8H,

J ) 5.2, 6.4 Hz, bpy-5,5′ of (iii)Re(bpy)(CO)₂-). ³¹P NMR (δ, 400

708 [M]⁴⁺, 993 [M + PF₆]³⁺

.

[Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}₃Re(bpy)(CO)₃](PF₆)₅,

[Re5ac]⁵⁺(PF₆^-)₅and [Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}₅Re-

(bpy)(CO)₃](PF₆)₇, [Re7ac]⁷⁺(PF₆^-)₇. A solution of CF₃SO₃salts

of [Re3ac]³⁺(150 mg, 0.06 mmol) in 200 mL of CH₂Cl₂was

irradiated for 1 h. About half of CH₂Cl₂was removed by

evaporation, and diethylether was added to the concentrated

solution. The precipitated red powder was ﬁltered off, washed with

diethylether, and then dried in a vacuum. A CH₂Cl₂solution (100

mL) containing the red powder (60 mg) and [Re2ac(η¹-

-

ac)₁]²⁺(CF₃SO₃

) (65 mg, 0.03 mmol) was stirred at room

2

temperature for 1 day, then at 40 °C for 1 day in dim light. The

solution was then evaporated. The residue was separated using SEC.

The bands that included products were collected and evaporated

under reduced pressure. A methanol solution of the residue was

added dropwise to a concentrated MeOH solution of NH₄PF₆. The

precipitated yellow powders were ﬁltered off, washed with dieth-

ylether, and dried in a vacuum. Yield: 32% ([Re5ac]⁵⁺) and 4%

([Re7ac]⁷⁺).

MHz, CD₃COCD₃): 7.54 (s), 7.14 (s), 2.56 (s). IR (MeCN): ν_CO

/

cm^-1) 2048 (m), 1956 (s), 1930 (m), 1885 (s). ESI FTMS in

MeCN (m/z): 750.6069 [M]⁸⁺, 878.4022 [M + PF₆]⁷⁺, 1048.9623

[M + 2(PF₆)]⁶⁺, 1287.7479 [M + 3(PF₆)]⁵⁺, 1645.9264 [M +

4(PF₆)]⁴⁺

.

Another Synthetic Method of [Re5ac]⁵⁺(PF₆^-)₅. A similar

procedure for [Re4ac]⁴⁺(PF₆^-)₄was applied to the synthesis of

[Re5ac]⁵⁺(PF₆^-)₅, using cis,trans-[Re(bpy)(CO)₂(η¹-ac)₂](CF₃SO₃)

instead of ac. Yield: 68%.

[Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}₁₀Re(bpy)(CO)₃](PF₆)₁₂,

-

[Re12ac]¹²⁺(PF₆

Re(bpy)(CO)₃](PF₆)₁₆, [Re16ac]¹⁶⁺(PF₆)₁₆. A solution of PF₆

)₁₂and [Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}₁₄-

-

salts of [Re4ac]⁴⁺(100 mg, 0.03 mmol) in 150 mL of MeCN was

irradiated for 1 h. About half of the MeCN was removed by

evaporation, and diethylether was added to the concentrated

solution. The precipitated red powder was ﬁltered off, washed with

diethylether, then dried in a vacuum. A THF/acetone (1:1) solution

(100 mL) containing 0.5 equiv each of the red powder (50 mg)

and ac (50 mg, 0.13 mmol) was stirried at room temperature for 1

day, then at 40 °C for 1 day in dim light. The solvent was

concentrated by evaporation, then diethylether was added to the

concentrated solution. The precipitated orange powder was ﬁltered

off, washed with diethylether, then dried in a vacuum. The resulting

orange solid (47 mg) and the remains of the red powder (50 mg)

were dissolved in 100 mL of a THF/acetone (1:1) solution and

stirred at room temperature for 1 day, then at 40 °C for 1 day in

dim light. The solution was then evaporated. PF₆salts of

[Re12ac]¹²⁺and [Re16ac]¹⁶⁺were isolated using a similar method

of [Re8ac]⁸⁺(PF₆^-)₈with 55% recovery of the starting complex

[Re4ac]⁴⁺(PF₆^-)₄.

[Re5ac]⁵⁺(PF₆^-)₅: Anal. Calcd for C₁₆₆H₁₂₀F₃₀N₁₀O₁₂P₁₃Re₅: C,

45.83; H, 2.78; N, 3.22. Found: C, 45.59; H, 2.77; N, 3.32. ¹H

NMR (δ, 400 MHz, CD₃COCD₃): 8.71 (d, 4H, J ) 5.2 Hz, bpy-

6,6′ of Re(bpy)(CO)₃-), 8.22 (d, 4H, J ) 8.0 Hz, bpy-3,3′ of

Re(bpy)(CO)₃-), 8.07 (dd, 4H, J ) 8.0, 7.6 Hz, bpy-4,4′ of

Re(bpy)(CO)₃-), 7.89 (d, 4H, J ) 5.6 Hz, bpy-6,6′ of (ii)Re(b-

py)(CO)₂-), 7.82 (d, 2H, J ) 5.2 Hz, bpy-6,6′ of (iii)Re(bpy)-

(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of (ii)Re(bpy)(CO)₂-),

7.63 (d, 2H, J ) 8.4 Hz, bpy-3,3′ of (iii)Re(bpy)(CO)₂-), 7.56 (dd,

4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of (ii)Re(bpy)(CO)₂-), 7.50 (dd, 2H,

J ) 8.4, 6.4 Hz, bpy-4,4′ of (iii)Re(bpy)(CO)₂-), 7.61-7.55 (m,

16H, Ph-p), 7.45-7.38 (m, 30H, Ph-m, and Ph-o), 7.36 (dd, 4H, J

) 7.6, 5.2 Hz, bpy-5,5′ of Re(bpy)(CO)₃-), 7.30-7.10 (m, 34H,

Ph-p, and Ph-o), 6.77 (dd, 4H, J ) 8.0, 5.6 Hz, bpy-5,5′ in

(ii)Re(bpy)(CO)₂-), 6.73 (dd, 2H, J ) 5.2, 6.4 Hz, bpy-5,5′ of

(iii)Re(bpy)(CO)₂-). ³¹P NMR (δ, 400 MHz, CD₃COCD₃): 7.51

(s), 7.14 (s), 2.56 (s). IR (MeCN): ν_CO/cm^-1) 2048 (s), 1963 (b),

1957 (s), 1930 (m), 1886 (s). ESI MS in MeCN (m/z): 725 [M]⁵⁺

944 [M + PF₆]⁴⁺

,

-

[Re12ac]¹²⁺(PF₆)₁₂: Yield 14% based on [Re4ac]⁴⁺(PF₆

)

4

.

used. Anal. Calcd for C₄₃₂H₃₁₆F₇₂N₂₄O₂₆P₃₄Re₁₂: C, 47.54; H, 2.92;

N, 3.08. Found: C, 47.77; H, 3.11; N, 3.04. ¹H NMR (δ, 400 MHz,

CD₃COCD₃): 8.71 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of Re(bpy)-

(CO)₃-), 8.22 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of Re(bpy)(CO)₃-), 8.07

(dd, 4H, J ) 8.4, 7.6 Hz, bpy-4,4′ of Re(bpy)(CO)₃-), 7.89 (d, 4H,

J ) 5.2 Hz, bpy-6,6′ of (ii)Re(bpy)(CO)₂-), 7.82 (d, 16H, J ) 5.2

Hz, bpy-6,6′ of (iii)Re(bpy)(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-

3,3′ of (ii)Re(bpy)(CO)₂-), 7.63 (d, 16H, J ) 8.4 Hz, bpy-3,3′ of

(iii)Re(bpy)(CO)₂-), 7.56 (dd, 4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of (ii)-

Re(bpy)(CO)₂-), 7.50 (dd, 16H, J ) 8.4, 6.4 Hz, bpy-4,4′ of

(iii)Re(bpy)(CO)₂-), 7.61-7.55 (m, Ph-p), 7.45-7.38 (m, Ph-m, and

Ph-o), 7.36 (dd, 4H, J ) 7.6, 5.2 Hz, bpy-5,5′ of Re(bpy)(CO)₃-),

7.30-7.10 (m, Ph-p, and Ph-o), 6.77 (dd, 4H, J ) 8.0, 5.2 Hz,

bpy-5,5′ in (ii)Re(bpy)(CO)₂-), 6.73 (dd, 16H, J ) 5.2, 6.4 Hz, bpy-

[Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}₄Re(bpy)(CO)₃](PF₆)₆,

[Re6ac]⁶⁺(PF₆^-)₆and [Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}₆Re-

(bpy)(CO)₃](PF₆)₈, [Re8ac]⁸⁺(PF₆^-)₈. A similar procedure for

-

[Re5ac]⁵⁺(PF₆

)

and [Re7ac]⁷⁺(PF₆

)

was applied to the

7

5

synthesis of [Re6ac]⁶⁺(PF₆

)

and [Re8ac]⁸⁺(PF₆^-)₈, using

6

-

[Re4ac]⁴⁺(PF₆^-)₄instead of [Re3ac]³⁺(PF₆^-)₃as precursor complex.

[Re6ac]⁶⁺(PF₆^-)₆: Yield 23% based on [Re4ac]⁴⁺(PF₆^-)₄used.

Anal. Calcd for C₂₀₄H₁₄₈F₃₆N₁₂O₁₄P₁₆Re₆: C, 46.33; H, 2.82; N,

1

3.18. Found: C, 46.60; H, 3.10; N, 2.94. H NMR (δ, 400 MHz,

CD₃COCD₃): 8.71 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of Re(bpy)-

(CO)₃-), 8.22 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of Re(bpy)(CO)₃-), 8.07

(dd, 4H, J ) 8.4, 7.6 Hz, bpy-4,4′ of Re(bpy)(CO)₃-), 7.89 (d, 4H,

J ) 5.2 Hz, bpy-6,6′ of (ii)Re(bpy)(CO)₂-), 7.82 (d, 4H, J ) 5.2

9

J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008 14673

A R T I C L E S

Yamamoto et al.

-

5,5′ of (iii)Re(bpy)(CO)₂-). IR (MeCN): ν_CO/cm^-1) 2048 (m),

1956 (s), 1930 (m), 1885 (s). ESI FTMS in MeCN (m/z): 946.5232

[Re15ac]¹⁵⁺(PF₆)₁₅: Yield 6% based on [Re5ac]⁵⁺(PF₆

)

5

used. Anal. Calcd for C₅₄₆H₄₀₀F₉₀N₃₀O₃₂P₄₃Re₁₅: C, 47.77; H, 2.94;

N, 3.06. Found: C, 47.80; H, 3.24; N, 2.76. ¹H NMR (δ, 400 MHz,

CD₃COCD₃): 8.71 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of Re(bpy)-

(CO)₃-), 8.22 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of Re(bpy)(CO)₃-), 8.07

(dd, 4H, J ) 8.4, 7.6 Hz, bpy-4,4′ of Re(bpy)(CO)₃-), 7.89 (d, 4H,

J ) 5.2 Hz, bpy-6,6′ of (ii)Re(bpy)(CO)₂-), 7.82 (d, 18H, J ) 5.2

Hz, bpy-6,6′ of (iii)Re(bpy)(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-

3,3′ of (ii)Re(bpy)(CO)₂-), 7.63 (d, 18H, J ) 8.4 Hz, bpy-3,3′ of

(iii)Re(bpy)(CO)₂-), 7.56 (dd, 4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of (ii)-

Re(bpy)(CO)₂-), 7.50 (dd, 18H, J ) 8.4, 6.4 Hz, bpy-4,4′ of

(iii)Re(bpy)(CO)₂-), 7.61-7.55 (m, Ph-p), 7.45-7.38 (m, Ph-m, and

Ph-o), 7.36 (dd, 4H, J ) 7.6, 5.2 Hz, bpy-5,5′ of Re(bpy)(CO)₃-),

7.30-7.10 (m, Ph-p, and Ph-o), 6.77 (dd, 4H, J ) 8.0, 5.2 Hz,

bpy-5,5′ in (ii)Re(bpy)(CO)₂-), 6.73 (dd, 18H, J ) 5.2, 6.4 Hz, bpy-

5,5′ of (iii)Re(bpy)(CO)₂-). IR (MeCN): ν_CO/cm^-1) 2048 (m),

1956 (s), 1930 (m), 1885 (s). ESI FTMS in MeCN (m/z): 1103.0469

[M + 2(PF₆)]¹⁰⁺, 947.6264 [M - CO + MeCN + 2(PF₆)]¹⁰⁺

,

1067.6893 [M + 3(PF₆)]⁹⁺, 1069.0260 [M - CO + MeCN +

3(PF₆)]⁹⁺, 1219.3965 [M + 4(PF₆)]⁸⁺, 1220.9002 [M - CO +

MeCN + 4(PF₆)]⁸⁺, 1414.3048 [M + 5(PF₆)]⁷⁺, 1415.8893 [M -

CO + MeCN + 5(PF₆)]⁷⁺

.

-

[Re16ac]¹⁶⁺(PF₆)₁₆: Yield 3% based on [Re4ac]⁴⁺(PF₆

)

4

1

used. H NMR (δ, 400 MHz, CD₃COCD₃): 8.71 (d, 4H, J ) 5.2

Hz, bpy-6,6′ of Re(bpy)(CO)₃-), 8.22 (d, 4H, J ) 8.4 Hz, bpy-3,3′

of Re(bpy)(CO)₃-), 8.07 (dd, 4H, J ) 8.4, 7.6 Hz, bpy-4,4′ of

Re(bpy)(CO)₃-), 7.89 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of (ii)Re(b-

py)(CO)₂-), 7.82 (d, 24H, J ) 5.2 Hz, bpy-6,6′ of (iii)Re(bpy)-

(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of (ii)Re(bpy)(CO)₂-),

7.63 (d, 24H, J ) 8.4 Hz, bpy-3,3′ of (iii)Re(bpy)(CO)₂-), 7.56

(dd, 4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of (ii)Re(bpy)(CO)₂-), 7.50 (dd,

24H, J ) 8.4, 6.4 Hz, bpy-4,4′ of (iii)Re(bpy)(CO)₂-), 7.61-7.55

(m, Ph-p), 7.45-7.38 (m, Ph-m, and Ph-o), 7.36 (dd, 4H, J ) 7.6,

5.2 Hz, bpy-5,5′ of Re(bpy)(CO)₃-), 7.30-7.10 (m, Ph-p, and Ph-

o), 6.77 (dd, 4H, J ) 8.0, 5.2 Hz, bpy-5,5′ in (ii)Re(bpy)(CO)₂-),

6.73 (dd, 24H, J ) 5.2, 6.4 Hz, bpy-5,5′ of (iii)Re(bpy)(CO)₂-). IR

(MeCN): ν_CO/cm^-1) 2048 (m), 1956 (s), 1930 (m), 1885 (s). ESI

FTMS in MeCN (m/z): 1077.1376 [M + 4(PF₆)]¹²⁺, 1078.2237

[M + 4(PF₆)]¹¹⁺, 1104.1411 [M - CO + MeCN + 4(PF₆)]¹¹⁺

,

1227.8493 [M + 5(PF₆)]¹⁰⁺, 1229.0525 [M - CO + MeCN +

5(PF₆)]¹⁰⁺, 1380.3828 [M + 6(PF₆)]⁹⁺, 1381.8322 [M - CO +

MeCN + 6(PF₆)]⁹⁺, 1571.0529 [M + 7(PF₆)]⁸⁺, 1572.8063 [M -

CO + MeCN + 7(PF₆)]⁸⁺

.

-

[Re20ac]²⁰⁺(PF₆)₂₀: Yield 4% based on [Re5ac]⁵⁺(PF₆

)

5

[M - CO + MeCN + 4(PF₆)]¹²⁺, 1188.2388 [M + 5(PF₆)]¹¹⁺

,

1

1189.4244 [M - CO + MeCN + 5(PF₆)]¹¹⁺, 1321.6564 [M +

6(PF₆)]¹⁰⁺, 1322.5600 [M - CO + MeCN + 6(PF₆)]¹⁰⁺, 1484.5049

used. H NMR (δ, 400 MHz, CD₃COCD₃): 8.71 (d, 4H, J ) 5.2

Hz, bpy-6,6′ of Re(bpy)(CO)₃-), 8.22 (d, 4H, J ) 8.4 Hz, bpy-3,3′

of Re(bpy)(CO)₃-), 8.07 (dd, 4H, J ) 8.4, 7.6 Hz, bpy-4,4′ of

Re(bpy)(CO)₃-), 7.89 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of (ii)Re(b-

py)(CO)₂-), 7.82 (d, 32H, J ) 5.2 Hz, bpy-6,6′ of (iii)Re(bpy)-

(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of (ii)Re(bpy)(CO)₂-),

7.63 (d, 32H, J ) 8.4 Hz, bpy-3,3′ of (iii)Re(bpy)(CO)₂-), 7.56

(dd, 4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of (ii)Re(bpy)(CO)₂-), 7.50 (dd,

32H, J ) 8.4, 6.4 Hz, bpy-4,4′ of (iii)Re(bpy)(CO)₂-), 7.61-7.55

(m, Ph-p), 7.45-7.38 (m, Ph-m, and Ph-o), 7.36 (dd, 4H, J ) 7.6,

5.2 Hz, bpy-5,5′ of Re(bpy)(CO)₃-), 7.30-7.10 (m, Ph-p, and Ph-

o), 6.77 (dd, 4H, J ) 8.0, 5.2 Hz, bpy-5,5′ in (ii)Re(bpy)(CO)₂-),

6.73 (dd, 32H, J ) 5.2, 6.4 Hz, bpy-5,5′ of (iii)Re(bpy)(CO)₂-). IR

(MeCN): ν_CO/cm^-1) 2048 (m), 1956 (s), 1930 (m), 1885 (s).

[M + 7(PF₆)]⁹⁺, 1485.9523 [M- CO + MeCN + 7(PF₆)]⁹⁺

,

1688.3134 [M + 8(PF₆)]⁸⁺, 1689.6658 [M - CO + MeCN +

8(PF₆)]⁸⁺, 1950.0658 [M + 9(PF₆)]⁷⁺, 1951.7845 [M - CO +

MeCN + 9(PF₆)]⁷⁺

.

[Re(bpy)(CO)₃(ac){Re(bpy)(CO)₂(ac)}_nRe(bpy)(CO)₃](PF₆)_n+2

-

(n ) 8, 13, and 18), [Re10ac]¹⁰⁺(PF₆)₁₀, [Re15ac]¹⁵⁺(PF₆)₁₅,

and [Re20ac]²⁰⁺(PF₆)₂₀. A similar procedure for PF₆salts of

-

[Re12ac]¹²⁺and [Re16ac]¹⁶⁺was applied to the synthesis of

[Re10ac]¹⁰⁺(PF₆)₁₀, [Re15ac]¹⁵⁺(PF₆)₁₅, and [Re20ac]²⁰⁺

-

(PF₆)₂₀, using PF₆salts of [Re5ac]⁵⁺instead of [Re4ac]⁴⁺(PF₆^-)₄.

50% of the starting complex [Re5ac]⁵⁺(PF₆^-)₅was recovered.

-

[Re10ac]¹⁰⁺(PF₆)₁₀: Yield 16% based on [Re5ac]⁵⁺(PF₆

)

-

5

used. Anal. Calcd for C₃₅₆H₂₆₀F₆₀N₂₀O₂₂P₂₈Re₁₀: C, 47.30; H, 2.90;

N, 3.10. Found: C, 47.52; H, 3.05; N, 3.07. ¹H NMR (δ, 400 MHz,

CD₃COCD₃): 8.71 (d, 4H, J ) 5.2 Hz, bpy-6,6′ of Re(bpy)-

(CO)₃-), 8.22 (d, 4H, J ) 8.4 Hz, bpy-3,3′ of Re(bpy)(CO)₃-), 8.07

(dd, 4H, J ) 8.4, 7.6 Hz, bpy-4,4′ of Re(bpy)(CO)₃-), 7.89 (d, 4H,

J ) 5.2 Hz, bpy-6,6′ of (ii)Re(bpy)(CO)₂-), 7.82 (d, 12H, J ) 5.2

Hz, bpy-6,6′ of (iii)Re(bpy)(CO)₂-), 7.72 (d, 4H, J ) 8.4 Hz, bpy-

3,3′ of (ii)Re(bpy)(CO)₂-), 7.63 (d, 12H, J ) 8.4 Hz, bpy-3,3′ of

(iii)Re(bpy)(CO)₂-), 7.56 (dd, 4H, J ) 8.4, 8.0 Hz, bpy-4,4′ of (ii)-

Re(bpy)(CO)₂-), 7.50 (dd, 12H, J ) 8.4, 6.4 Hz, bpy-4,4′ of

(iii)Re(bpy)(CO)₂-), 7.61-7.55 (m, Ph-p), 7.45-7.38 (m, Ph-m, and

Ph-o), 7.36 (dd, 4H, J ) 7.6, 5.2 Hz, bpy-5,5′ of Re(bpy)(CO)₃-),

7.30-7.10 (m, Ph-p, and Ph-o), 6.77 (dd, 4H, J ) 8.0, 5.2 Hz,

bpy-5,5′ in (ii)Re(bpy)(CO)₂-), 6.73 (dd, 12H, J ) 5.2, 6.4 Hz, bpy-

5,5′ of (iii)Re(bpy)(CO)₂-). IR (MeCN): ν_CO/cm^-1) 2048 (m),

1956 (s), 1930 (m), 1885 (s).

Acknowledgment. We thank Dr. Shigeru Sakamoto (Thermo

Fisher Scientiﬁc) for ESI FTMS measurements.

Supporting Information Available: Crystallographic ﬁles for

the PF₆^-salts of [Re2ac]²⁺, [Re3ac]³⁺, [Re3et]³⁺, and [Re4-

et]⁴⁺in CIF format; crystallographic data; ESI MS spectra of

[Re2ac]²⁺and [Re4ac]⁴⁺before and after irradiation; chro-

matograms of analytical SEC of reaction mixture and isolated

[Re5ac]⁵⁺, [Re10ac]¹⁰⁺, [Re15ac]¹⁵⁺, and [Re20ac]²⁰⁺; pack-

ing diagram of [Re2ac]²⁺(PF₆^-)₂; Figure S5, emission decay

curve of [Re8ac]⁸⁺. This material is available free of charge

via the Internet at http://pubs.acs.org.

JA8044579

9

14674 J. AM. CHEM. SOC. VOL. 130, NO. 44, 2008

Article Doi

Systematic synthesis, isolation, and photophysical properties of linear-shaped Re(I) oligomers and polymers with 2-20 units

DOI: 10.1021/ja8044579

Source and publish data:

Authors:

Article abstract of DOI:10.1021/ja8044579

Full text of DOI:10.1021/ja8044579

Products guided by the article

R&D Labs maybe for 1073530-40-1

Relevant to this article

Hot Product