When food is available recurrently at a particular time of day, several species increase their locomotion in the hours that precede food delivery, a phenomenon called food anticipatory activity (FAA). In mammals, many studies have shown that FAA is driven by a food-entrained circadian oscillator (FEO) that is distinct from the light-entrained pacemaker in the suprachiasmatic nucleus of the hypothalamus. Few studies have investigated the effect of sugar ingestion on food anticipatory rhythms and the FEO. We aimed to extend the understanding of the role of glucose on the emergence of food anticipatory rhythms by investigating whether glucose ingestion is sufficient to produce daily food anticipation, reflected by motor activity and core body temperature rhythms. Under a 12 h/12 h light/dark cycle, chow-deprived rats had glucose solution available between Zeitgeber Time (ZT) 6 and ZT 9 for 10 days (glucose restriction group), whereas control animals had chow available within the same time window (chow restriction group). Animals in both groups exhibited anticipatory motor activity and body temperature around the fourth day of the scheduled food restriction. Glucose-fed rats ingested ~15 kcal on the days immediately before FAA emergence and reached an intake of ~20 kcal/day, whereas chow-fed rats ingested ~40 kcal/day. The glucose restriction group exhibited a pattern of food anticipation (activity and temperature) that was extremely similar to that observed in the chow restriction group. We conclude that glucose ingestion is a sufficient temporal cue to produce recurrent food anticipation, reflected by activity and temperature rhythms, in rats.

A investigação das estruturas em solução dos compostos [Ir4(CO)11L] [L = [Fe(eta5-P3C2Bu t2) (eta5-C5H5)] (1) e [Fe(eta5-P3C2Bu t2)(eta5-P2C 3Bu t3)] (2)], por espectroscopia de RMN de 13C e de 31P, mostrou que, a 163 K, o composto 1 existe na forma de dois isômeros, um deles contendo carbonilas em ponte e o outro, carbonilas terminais, na razão de 1:0,15, respectivamente, enquanto que o composto 2 existe somente na forma do isômero contendo carbonilas em ponte. À temperatura ambiente, somente no composto 2 ocorre um deslocamento 1,2 do anel eta5-P3C2Bu t 2. Enquanto o composto 2 sofre fácil dissociação de CO em solução para dar [Ir4(CO)10{mi-eta¹-eta¹-[Fe(eta5-P3C2 Bu t2)(eta5-P2 C3Bu t3)}] (3), foi necessário usar Me3NO para produzir [Ir4(CO)10{[Fe(eta5-P 3C2Bu t2)(eta5-C5H5)}] (4) a partir de 1. Este composto foi obtido sob a forma de dois isômeros interconversíveis, 4a e 4b, que não puderam ser separados. Um estudo de difração de raios-X do isômero 4a mostrou que o ligante [Fe(eta5-P3C2Bu t2) (eta5-C5H5)] encontra-se ligado em ponte a uma das arestas do tetraedro de Ir4, interagindo através do par de elétrons livres de um dos átomos de fósforo adjacentes e de modo eta²- através da ligação dupla P=P do anel eta5-P3C2Bu t 2 e que todos os ligantes CO encontram-se ligados de modo terminal. Um estudo de RMN de 31P{¹H} a várias temperaturas evidenciou um processo fluxional que envolve as interações entre os átoms de Ir1 e Ir2 e o par de elétrons livres no átomo P1, a ligação P1-P2 e o par de elétrons livres no átomo P2. De acordo com os dados de RMN multinuclear, a estrutura do cluster 4b é semelhante à do composto 3, com o anel eta5-P3C2Bu t 2 coordenado de modo eta¹-eta¹- através dos dois átomos de P adjacentes e com todos os ligantes CO ligados de modo terminal.

Investigation of the solution structures of [Ir4(CO)11L] (L = [Fe(eta5-P3C2Bu t2)(eta5-C5H 5)] (1) and [Fe(eta5-P3C2Bu t2)(eta5-P2C 3Bu t3)] (2) by 13C and 31P NMR spectroscopy showed that, at 163K, 1 exists in the form of two isomers with bridged and non-bridged structures, in a 1:0.15 ratio, respectively, whereas 2 exists only in the bridged form. At RT, 1,2 shift of the eta5-P3C2Bu t 2 ring was only observed for compound 2. Where as 2 loses CO readily in solution to give [Ir4(CO)10{mu-eta¹-eta¹-[Fe(eta5-P3C2 Bu t2)(eta5-P2 C3Bu t3)}] (3), activation with Me3NO was necessary to produce [Ir4(CO)10{[Fe(eta5-P 3C2Bu t2)(eta5-C5H5)}] (4), obtained in the form of two non-interconverting isomers 4a and 4b, which were not able to be separated. A single crystal X-ray diffraction study of isomer 4a established that the [Fe(eta5-P3C2Bu t2)(eta5-C5H 5)] ligand bridges one of the edges of the Ir4 tetrahedron, interacting via the lone electron pair of one of the adjacent P atoms and in an eta²- mode via the P-P double bond of the eta5-P3C2Bu t 2 ring and that all CO ligands are terminally bonded. Variable temperature 31P{¹H} NMR spectroscopy evidenced a fluxional process involving interactions between the Ir1 and Ir2 atoms and the lone pair on P1, the P1-P2 bond, and the lone pair on P2. According to multinuclear NMR, cluster 4b has similar structure to compound 3, with the eta5-P3C2Bu t 2 ring co-ordinated in a eta¹-eta¹- mode via the two adjacent P atoms, and all CO ligands bonded terminally.

A reação de [Ir4(mi-H)(CO)9(Ph2PC<FONT FACE=Symbol>º</FONT>CPh)(mi-PPh2)] 1 com P<FONT FACE=Symbol>º</FONT>CBu t em CH2Cl2 a 35 °C por 4 h leva à formação do composto inédito [Ir4(mi-CO)(CO)7{mi4-eta³-Ph2PC(H)C(Ph)PCBu t}(mi-PPh2)] 2, que contem a cadeia 2-fosfabutadienilfosfina. O composto 2 forma-se também quando [Ir4(CO)10(Ph2PC<FONT FACE=Symbol>º</FONT>CPh)(PPh2H)] 3 é aquecido na presença de P<FONT FACE=Symbol>º</FONT>CBu t, em thf, a 40 °C, por 48 h. Essas duas reações também produzem pequenas quantidades de [Ir4(mi-CO)(CO)7(mi3-eta²-HCCPh)(mi-PPh2)2] 4, porque as velocidades das transformações de 1 e de 3 em 4 e das reações desses compostos com P<FONT FACE=Symbol>º</FONT>CBu t são semelhantes. O composto 2 foi caracterizado por dados analíticos e espectroscópicos, espectrometria de massas usando fonte de FAB e experimentos de RMN de ¹H, 31P, 13C, 2D 31P-¹H HETCOR, diferença de nOe e DEPT que levaram à sua formulação e estabeleceram que havia ocorrido o acoplamento entre o ligante Ph2PC<FONT FACE=Symbol>º</FONT>CPh e o P<FONT FACE=Symbol>º</FONT>CBu t e a migração do hidreto para o Calfa do Ph2PC<FONT FACE=Symbol>º</FONT>CPh. Entretanto, esses dados não permitiram decidir se a clivagem da ligação P-Csp do Ph2PC<FONT FACE=Symbol>º</FONT>CPh havia ocorrido e nem definir o modo de interação da cadeia organofosforada. A estrutura molecular do composto 2, determinada por uma análise de difração de raios-X, mostrou que o cluster exibe um arranjo metálico na forma de uma borboleta e que a cadeia organofosforada, corretamente formulada por dados espectroscópicos, interage com o poliedro metálico através de quatro ligações sigma.

Reaction of [Ir4(mu-H)(CO)9(Ph2PC<FONT FACE=Symbol>º</FONT>CPh)(mu-PPh2)] 1 with P<FONT FACE=Symbol>º</FONT>CBu t in CH2Cl2, at 35 °C, for 4 h yields the novel compound [Ir4(mu-CO)(CO)7{mu4-eta³-Ph2PC(H)C(Ph)PCBu t}(mu-PPh2)] 2, which contains the 2-phosphabutadienylphosphine chain. Compound 2 is also formed upon thermolysis of [Ir4(CO)10(Ph2PC<FONT FACE=Symbol>º</FONT>CPh)(PPh2H)] 3 in the presence of P<FONT FACE=Symbol>º</FONT>CBu t in thf, at 40 °C, for 48 h. Small amounts of [Ir4(mu-CO)(CO)7(mu3-eta²-HCCPh)(mu-PPh2)2] 4 are always obtained from both reactions, because of the competing rates of the transformations of 1 and 3 into 4 and of their reactions with P<FONT FACE=Symbol>º</FONT>CBu t. Compound 2 was characterized by analytical and spectroscopic studies such as FAB ms, ¹H, 31P,13C, 2D31P-¹H HETCOR, nOe difference and DEPT NMR experiments, which led to its formulation and established the coupling between the coordinated Ph2PC<FONT FACE=Symbol>º</FONT>CPh and P<FONT FACE=Symbol>º</FONT>CBu t and the migration of the hydride to the Calpha of the Ph2PC<FONT FACE=Symbol>º</FONT>CPh ligand. However, it was impossible to establish unambiguously if cleavage of the P-Csp bond of the Ph2PC<FONT FACE=Symbol>º</FONT>CPh ligand had occurred and the mode of interaction of the organophosphorus chain. An X-ray diffraction study of compound 2 established a butterfly arrangement of iridium atoms with the new ligand interacting with the metal framework via four sigma bonds and the PPh2 phosphorus lone pair.