Chapter 22
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Functionalized Polydiacetylenes with Polar, Hydrogen Bonding and Metal-Containing Groups I. H. Jenkins, W. E. Lindsell, C. Murray, P. N. Preston, and T. A. J. Woodman Department of Chemistry, Heriot-Watt University, Riccarton, Edinburgh, EH14 4AS, United Kingdom
New polydiacetylenes (PDAs) have been synthesized either by U V or y-irradiation of diacetylenes or by 'polymer analogous' reactions of suitable precursors. PDAs with platinum moieties coordinated to the backbone have been synthesized and characterized by reference to novel, metallated oligomeric enynes. Metal-containing groups (e.g. Ru, Mo, N i , Cu) have also been attached to PDAs through suitably functionalized side-chains, e.g. phosphinyl, (dialkyl)amino and bipyridyl groups. New diacetylenes incorporating the bases of D N A (adenine, thymine, cytosine) have been synthesized but in general do not polymerize by γ-irradiation. Nevertheless, thymine- and cytosine -containing PDAs have been characterized. The nonlinear optical properties of selected functionalized PDAs have been studied by the z -scan technique.
Certain diacetylenes (1; R = e.g. aryl, functionalized alkyl) undergo a solid state (topochemical) polymerization induced by heat, U V or gamma radiation to give polydiacetylenes (PDAs) (2);^ the process only occurs if the molecules are properly aligned, with a critical repeat distance near 5.OA and an orientation angle ca. 45° relative to the translation axis. PDAs are highly coloured, often red or purple insoluble materials, but many, including polymers resulting from diacetylenes with urethane, sulfonate, or carboxylic acid ester ' side-chains, are soluble in common organic solvents. An interesting feature of some PDAs is their property of chromism which can be manifested in bulk samples as thermo- and photo-chromism; soluble PDAs can also show thermochromic effects in solution, and a related solvatochromism is observed on variation of the solvent to non-solvent ratio. An intriguing feature of PDAs containing carboxylic acid groups [2; R = (CH2) C02H; n = e.g. 2, 3, 8] is the effect of pH changes on absorption spectra {acids (2) are yellow 2
3
4
5 6
7
n
©1998 American Chemical Society In Functional Polymers; Patil, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.
321
322 8
in alkaline solution but red in acid}. The origin of such dichromism probably relates to a change in effective conjugation length and, for certain PDAs, an aggregation phenomenon. * 9
41
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R
There have been recent significant advances in connection with the manner in which chromic effects in PDAs can be harnessed for potential applications in biosensor technology. Charych, Bednarsky et al. recognised that a chromic effect in certain PDAs can arise from the influence on the backbone chromophore of subtle conformational effects within a Langmuir-Blodgett bilayer assembly containing a receptor binding ligand (sialic acid analogue) specific to viral hemagglutinin. Exposure of the assembly to influenza virus elicits a colour change from blue to red. A more convenient colorimetric procedure for this assay has subsequently been devised using P D A liposomes derived from diacetylenes. More recently, paramagnetic P D A liposomes have been characterised, and applications of such materials for magnetic resonance imaging can be anticipated. PDAs are also promising candidates for incorporation into optical devices on account of their large third order susceptibilities ( x ~ 10" - 10" esu). ' The ultrafast non-resonant refractive nonlinearities of PDAs are amongst the largest of any materials, and the resonant nonlinearities (orders of magnitude larger) have timescales of the order of picoseconds, which closely match the likely shortest practical pulse durations of optical communication and processing systems. The figures-ofmerit for all-optical mechanisms (switching, directional-coupling) in PDAs continue to offer the prospect that usable devices could be fabricated. Most optical measurements have been carried out on thin solid films, but soluble PDAs (see above) also show significant x values in solution. 10
11
12
3
3
9
10
13
14
15
Objectives and Technological Relevance of the Programme The extended conjugation of the PDA backbone is undoubtedly responsible for the extraordinary optical nonlinearity observed in such materials. In our programme we have attempted to modify the 'effective conjugation length' in PDAs in two ways. First, we have modified the unsaturated enyne polymer backbone by metallation, and characterized the ensuing materials by reference to model organometal lies prepared from oligomeric conjugated enynes. Secondly, in the light of studies by Patel and ourselves, we have considered whether the unusual properties of PDA carboxylic acids might be manifested in related ionomeric materials. The following groups of PDAs have featured in our studies: 9
8
(a) Metallated PDAs involving r\-bonding of metals to alkyne moieties of the polymer backbone. (b) PDAs with ligating groups, e.g. diphenylphosphinyl, dialkylamino and 2,2'bipyridyl, incorporated into the side-chains, and metallated species derived therefrom. (c) PDAs with side-chains incorporating ammonium, phosphonium and zwitterionic groups.
In Functional Polymers; Patil, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.
323 (d) PDAs containing appropriate specific pairwise combinations of DNA bases, the combinations being chosen so that H-bonded interactions can occur between separate PDAs or in assemblies of monomers prior to polymerisation. Interactions of such functionalized PDAs with other compatible substrates are also of interest. Synthetic Studies Metallated PDAs and Model Compounds. We have already reported metallated 'model' enynes (e.g. 3-5) related to PDAs. Downloaded by UNIV OF MICHIGAN ANN ARBOR on June 18, 2013 | http://pubs.acs.org Publication Date: May 8, 1998 | doi: 10.1021/bk-1998-0704.ch022
16
M,L, 2^n
M
2 n
( 3 ) M L„ = Co (CO)«; M (CO) (il-C5H )2, (M = Mo, W)
L
2
2
2
4
5
(OQ3C0—Co(CO)
Ph
( O C ) C o ' — Co(CO) 3
3
3
(OC) C—Co(CO) 3
3
(4)
(OC) Co—Co(CO)
Ph
3
3
(CO) Co—Co(CO) 3
(OC)jCo'
Co(CO)
3
3
Ph (OC) Co—Co(CO) 3
3
(5) The above organometallic complexes have been used to aid spectroscopic characterization of novel metallated PDAs (e.g. 6) . 17
(OC) Co 3
FV\ / _ \ \
R
1
2
(6a) R - R - ( C H ) 0 C C H P h C H )), 0 C C H P h (6b) R = (CH ),CH , R = ((CH 2
9
1
Co(CO)
2
2
2
2
3
22
2
2
3
More recently we have prepared analogous platinum containing enynes (e.g. 7,8) and achieved up to 35% metallation of the alkyne component of the PDA backbone in reactions with [Pt(ti -C2H4)(PPh3)2] (see 9). 2
18
In Functional Polymers; Patil, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.
324 Ph,P,
,PPh
/
"3 \ r
3
Pt
Ph-=?s pt ph p
/
s
3
pph
Ph 3
Pt (7)
Ph P Downloaded by UNIV OF MICHIGAN ANN ARBOR on June 18, 2013 | http://pubs.acs.org Publication Date: May 8, 1998 | doi: 10.1021/bk-1998-0704.ch022
3
,PPh
v
PPh
3
3
3
Pt I
Ph-
Ph P
Ph P 3
N
3
Pt
I Pt Pl^p'
,PPh
N
pPh
Ph 3
Pt Ph P
(8)
7
X
3
pPh
3
K I Pt
R (9) N
Ph P 3
p
P h
R - e.g. ( C H ) 0 C C H P h 2
9
2
2
,
Metallated Materials derived from PDAs with Phosphine-, Amine- and Bipyridyl-terminated Side-chains. We prepared bis(diphenylphosphinyl)diynes (10a - c) but found that they do not polymerize under the influence of y- or UVirradiation, and form PDAs in only very low conversions by thermal treatment. 7
R(CH ) 2
R(CH )„
4
(CH ) R
2
2
n
(CH ) R 2
(10)
a b c d
R = PPh , n = 2 R = PPh , n = 3 R = PPh , n = 4 R = PPh {Mo(CO) }, n - 4 2
(11)
2
2
2
5
a b c d
4
R = PPh R = OTs R = PPh Mo(CO) or PPh R = NEt 2
2
5
2
2
Accordingly, the phosphinated PDA (11a) was prepared using a method related to that of Kiji et a/., by reaction of the PDA tosylate (lib, PTS-12) with diphenylphosphinyl-potassium or -lithium. A model, metallated diyne (lOd) has recently been prepared from (10c) and [Mo(CO)5(THF)], and a 'polymer analogous' reaction has generated the partially metallated PDA (11c); e.g. P{ H} NMR 19
20
3,
,
(CDC1 ): (lOd) 28.7 ppm; (11c) 28.4 ppm; IR v(CO) (CHCI3): (lOd) 2071, 1986, 3
1
1
1945 cm" ; (11c) 2072, 1983, 1944 cnr (+ weaker bands from some bis(phosphine)tetracarbonyl molybdenum sites).
In Functional Polymers; Patil, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.
325 It also proved necessary to prepare PDAs with (dialkylamino)alkyl side-chains through polymer analogous reactions. Thus (lid) was prepared from (lib) and diethylamine and the former has recently been converted into water soluble complexes (12 a, b) by treating the PDA (lid) with nickel(II) and copper(II) chloride, respectively, in varying stoichiometrics. 20
2+
M(aq) NEt2
